Prep the pan and oven: Preheat oven to 350°F (175°C). Grease a 9-inch round cake pan, line the bottom with parchment, and lightly flour the sides. This helps the cake release cleanly.
Whisk the dry ingredients: In a medium bowl, whisk 1 cup all-purpose flour, 1 cup almond flour, 1 1/2 teaspoons baking powder, 1/4 teaspoon baking soda, and 1/2 teaspoon fine sea salt.
Set aside.
Cream the butter and sugar: In a large bowl, beat 1/2 cup (1 stick) softened unsalted butter with 3/4 cup granulated sugar on medium-high until pale and fluffy, about 2–3 minutes. Proper creaming traps air for a lighter crumb.
Add the eggs and extracts: Beat in 3 large eggs, one at a time, mixing well after each. Stir in 1 teaspoon almond extract and 1 teaspoon vanilla extract.
Scrape the bowl so everything combines evenly.
Mix in the sour cream: Add 1/2 cup sour cream and beat until smooth. The batter should look creamy and thick.
Alternate dry ingredients and milk: On low speed, add half the dry mixture, then 1/3 cup whole milk, then the remaining dry mixture. Mix just until combined.
Do not overmix.
Pan and topping: Spread the batter into the prepared pan. Smooth the top. If you like, sprinkle 1/4 cup sliced almonds over the surface for a delicate crunch.
Bake: Bake for 28–34 minutes, until the top is lightly golden and a toothpick inserted in the center comes out clean or with a few moist crumbs.
Start checking at 28 minutes.
Cool: Let the cake cool in the pan for 10 minutes, then run a knife around the edge and invert onto a rack. Peel off the parchment and flip upright to cool completely.
Finish and serve: Dust with powdered sugar or drizzle with a simple glaze (powdered sugar thinned with milk and a drop of almond extract). Serve plain or with fresh berries and whipped cream.