Let Me Tell You About This Blueberry Cake (Yes, You Want This Recipe)

There are some nights when you just want cake and nothing else will do. A few years ago (was it 2018? I don't know, time gets blurry), I started messin' around with the classic Kentucky butter cake recipe after my best mate went keto and got a bit cranky about missing desserts. The first attempt was... well, let's say the dog enjoyed it more than we did. But after much tinkering—and a wild notion to toss in a handful of slightly sad blueberries—this low carb, keto-friendly blueberry butter cake emerged. Now I can't make it without someone popping 'round and 'politely' demanding a slice.

Low Carb (Keto-Friendly) Blueberry Butter Cake

And look: I still call my oven 'temperamental Bertha' so if you ever burned the top or undercooked the middle, you're in solid company.

Why You'll Love This (If My Family's Anything to Go By!)

Honestly, I make this when a craving for something sweet hits but I'm also trying (desperately) to stick to foods that don't make me feel like a hibernating bear afterwards. My family loves it because it's rich and buttery but doesn't smack you with sugar—like some cakes do; you know what I mean. Oh, and I discovered, after making it for a brunch, that it's one of those cakes which—if you leave it on the counter—will mysteriously disappear, one forkful at a time. The blueberries just kind of pop and melt into pockets of jammy goodness (I do get a bit passionate about those berries, if we're honest). If you’re avoiding carbs or just want something not too sweet, here you go. I used to be frustrated because almond flour cakes can taste a bit gritty or dry—but not this one, promise.

What You'll Need (Or What I Throw In When I'm Out of Something)

2 cups almond flour (my gran swears by Bob's Red Mill, but I've used supermarket stuff and it's fine)
½ cup coconut flour (totally skip and use more almond flour if you hate coconut; works almost as well!)
½ cup unsalted butter, melted—okay, I know I should say room temp, but who's got the patience?
¾ cup erythritol (or allulose, monk fruit, or—even a blend. Once I used half Swerve, seemed okay.)
4 large eggs
½ cup sour cream (I sometimes swap Greek yogurt if I forgot the sour cream—no one noticed... yet)
1 teaspoon vanilla extract (sometimes I add a splash more—oops!)
½ teaspoon baking powder
¼ teaspoon salt—unless you're using salted butter, then maybe a tiny pinch or none
1 teaspoon lemon zest (optional—but super nice if you remember)
¾ cup fresh blueberries (I’ve used frozen too... just don’t thaw or it turns purple. Unless you like purple cake!)

Directions (AKA: How I Actually Get This Into the Oven)

Preheat your oven to 350°F (that’s 175°C for the metric folks who do things properly). Grease an 8-inch round or square cake pan. I line with parchment if I remember, which is about half the time.
Whisk almond flour, coconut flour, baking powder, salt (and lemon zest if you're feeling fancy) in a bowl. Nothing special—just get them mingling.
In another bowl, beat the eggs with the sweetener until, well, kinda creamy. Add melted butter, sour cream, and vanilla extract. Beat again until combined. It’ll look... odd. Don’t fret.
Mix the wet stuff into the dry. This is the part where I always worry it’ll be too thick, but go with it! Fold until just mixed.
Gently fold in the blueberries. Save a few to scatter on top if you want Instagram points; I usually forget.
Spoon the batter into the pan and smooth the top. Don’t stress if it’s lumpy—it sorts itself out.
Bake for 35–40 minutes (but keep an eye on it after 30, every oven is a wild animal). When it’s golden and a skewer comes out tidy (ish), it’s done. Cool for at least 15 minutes before cutting—or way longer if you don’t enjoy eating hot cake straight from the pan (I do).

What I've Learned the Messy Way (Notes)

If you use only almond flour, the cake is denser. Tasty, but—on second thought—maybe add a touch more baking powder if you try that.
I once mixed in frozen blueberries without rinsing them and ended up with a tie-dye cake. It tasted fine, but wow, the color.
Don’t panic if the batter looks very thick. It always does. I think it’s just a low carb thing.

Swaps and Experiments (A Few Surprises Here!)

Strawberries instead of blueberries? Totally works, but dice 'em smaller or they're a bit chunky.
Lemon icing—once tried it with lemon juice/erythritol glaze. It was... okay, but honestly made the cake too sweet for me.
I tried adding shredded coconut. Meh. Didn't love it. But you might!

Do You Need Fancy Equipment?

Look, a stand mixer is nice but I've made this with nothing but a big fork and a sturdy arm; it's a cake, not brain surgery. If you don’t have a parchment sheet, straight butter and a little almond flour dusted in the pan work just fine.

How I Attempt to Store It (With Mixed Success)

In theory, store leftovers in an airtight container at room temp for a couple days or the fridge for up to a week. But honestly, in my house it never makes it past the next breakfast. And I think it actually tastes nicer the next day, if you can manage that little miracle.

Serving This Up (A Family Quirk or Two)

We like a little dollop of whipped cream or a tiny spoonful of Greek yogurt. My cousin insists on eating it with his morning coffee, which is a bit odd if you ask me… but to each their own. Once, I even warmed up a slice and topped it with a smidge of sugar-free ice cream (highly recommended on hot days).

My Hard-Earned Pro Tips (AKA Don't Make My Mistakes)

Don’t rush the cooling, impatient as you might be. I once sliced right away and it crumbled like sand at the beach. Wait it out. (Or at least go get distracted for 15 minutes.)
Don’t double the blueberries unless you enjoy blueberry soup. Trust me on that one!

Now For the Random Questions (You Actually Might Have)

Can I make this nut-free?: Not easily—in fact, I tried using sunflower seed flour once and it went a bit green (science is wild). I'd stick with almond flour unless you're feeling adventurous.
Do I have to use a cake pan?: Honestly, I’ve made this in a loaf pan, even muffin tins. So, do what suits you. Just watch the bake time. Muffins are done way quicker!
Why is my cake a bit dry?: Probably overbaked. Or, sometimes coconut flour is a bit thirsty. Next time, a smidge more sour cream (or yogurt) can save the day.
Is this super sweet?: Nope—it’s more like a coffee cake level sweet. If you want it sweeter, just add a few more tablespoons of sweetener. Or not.
Can I freeze it?: Yeah, slices freeze fine. But, wrap well—unless you like freezer burn, which I do not recommend. That’s about it.

Let me know if you try it! Or just let your family guess if it’s really keto—they never believe me anyway.

Low Carb (Keto-Friendly) Blueberry Butter Cake