Preheat oven to 325°F (170°C).

In the bowl of a stand mixer fitted with the paddle attachment, beat butter and sugars at medium-low speed just until combined. Increase mixer speed to medium; beat until fluffy, 3 to 4 minutes, stopping to scrape sides of bowl. Add egg and egg yolk, one at a time, beating well after each addition. Beat in extracts.

In a large bowl, whisk together flour, salt, and baking powder. With mixer on low speed, gradually add flour mixture to butter mixture alternately with buttermilk, beginning and ending with flour mixture, beating just until combined after each addition. Gently fold in 1/3 cup (64 grams) sprinkles.

Spray a tall-sided 10-inch fluted round removable-bottom tart pan with baking spray with flour. Spoon batter into prepared pan, smoothing top with a small offset spatula. Sprinkle remaining 1 tablespoon (10 grams) sprinkles on top.

Bake until a wooden pick inserted in center comes out clean, 30 to 35 minutes. Let cool in pan for 10 minutes. Carefully remove sides of pan; let cool completely on pan base on a wire rack.

Using a large offset spatula, carefully loosen cake from pan base; place cake on a serving plate. Spoon Vanilla-Almond Buttercream into a pastry bag fitted with a coupler; pipe buttercream on top of cooled cake using assorted small piping tips (Wilton No. 10, Wilton No. 21, Wilton No. 199). Garnish with sprinkles, if desired.