Brown sugar stars in this drop-dead-scrumptious dessert, adding depth and complexity to everything from the yellow cake layers to the creamy caramel filling and cream cheese frosting. Use a candy thermometer to give the caramel proper flavor and consistency–get it right, and this cake could make your reputation as a baker.
Preheat oven to 350°. Grease 2 (9-inch) round cake pans; line with lightly greased parchment or wax paper.
Combine flour, baking powder, and salt in a bowl; set aside. Place 1 3/4 cups granulated sugar, 1/4 cup light brown sugar, and 1 cup butter in a large bowl; beat with a mixer at medium speed 5 minutes or until well blended. Add eggs, 1 at a time, beating well after each addition. Stir in vanilla. Add flour mixture and 1 cup milk alternately to butter mixture, beginning and ending with flour mixture and beating at low speed after each addition. Pour into prepared pans; sharply tap pans once on counter to remove air bubbles. Bake at 350° for 35 minutes or until wooden pick inserted in center comes out clean. Cool in pans on wire rack 10 minutes; remove from pans, and cool completely on wire rack. Place 1 layer on a cake plate.
Combine 1 1/2 cups brown sugar, evaporated milk, and 1/4 cup butter in a saucepan. Cook over medium heat, stirring until sugar is dissolved. Cook (without stirring) until a candy thermometer registers 238°. Transfer to a heat-resistant bowl, and beat 3 minutes or until thickened and easy to spread. Quickly spread filling over cake layer on plate. Cover loosely with plastic wrap; chill 15 minutes or until set.
Spread a thin layer of Caramel Cream Cheese Frosting over filling. Top with second layer. Frost cake. Chill 20 minutes or until frosting sets, then cover and chill 4 hours or overnight. Let stand 10 minutes at room temperature before serving. Garnish, if desired.