Preheat the oven to 350°F (175°C). Grease a 9-inch round pan and line the bottom with parchment. Pro-level move: tap the pan to settle any air pockets and give it a quick spray of nonstick spray.

In a bowl, whisk together flour, baking powder, baking soda, and salt. This is your dry squad—keep them organized and away from the butter, please.

In another bowl, cream butter and sugar until light and fluffy. This usually takes 2–3 minutes with an electric mixer. Scrape the sides, add the eggs one at a time, and beat until incorporated.

Beat in sour cream, milk, lemon zest, and lemon juice until the batter looks bright and glossy. Don’t overmix; you’re aiming for a tender crumb, not a trampoline.

Gently fold in the dry ingredients until just combined. It’s okay if you still see a few flour streaks—overworking = tougher cake.

Carefully fold in the blackberries, saving a handful for garnish if you want a photo-worthy slice. The batter will be speckled with purple; that’s flavor drama you didn’t know you needed.

Pour batter into the prepared pan and bake for 34–38 minutes, or until a toothpick inserted in the center comes out with just a few moist crumbs. Do a little dance if you want—your cake deserves celebratory vibes.

Let the cake cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. If you’re impatient, the cooling might be the toughest part, but you’ve got this.

(Optional) Whisk together powdered sugar and lemon juice for a glaze. Drizzle over cooled cake for a glossy finish. Garnish with reserved blackberries if you’re feeling extra.