Blueberry topping
3/4 cup (packed) golden brown sugar
1/2 cup (1 stick) unsalted butter, cut into 4 pieces
1 1/2 cups fresh blueberries

Lemon-almond butter cake
3/4 cup cake flour
1/4 teaspoon baking powder
1/4 teaspoon fine sea salt
4 ounces almond paste (scant 1/2 cup), broken into small pieces
1/2 cup sugar
3 tablespoons finely grated lemon peel
1/2 cup (1 stick) unsalted butter, cut into 8 pieces, room temperature
3 large eggs, room temperature

Lemon slices (optional)
Lemon peel curls (optional)
Additional fresh blueberries

1 cup chilled heavy whipping cream
2 tablespoons sugar
1 tablespoon finely grated lemon peel
2 teaspoon fresh lemon juice

3/4 cup (packed) golden brown sugar 1/2 cup (1 stick) unsalted butter, cut into 4 pieces 1 1/2 cups fresh blueberries 3/4 cup cake flour 1/4 teaspoon baking powder 1/4 teaspoon fine sea salt 4 ounces almond paste (scant 1/2 cup), broken into small pieces 1/2 cup sugar 3 tablespoons finely grated lemon peel 1/2 cup (1 stick) unsalted butter, cut into 8 pieces, room temperature 3 large eggs, room temperature 1 cup chilled heavy whipping cream 2 tablespoons sugar 1 tablespoon finely grated lemon peel 2 teaspoon fresh lemon juice

For blueberry topping:
Preheat oven to 350°F. Combine brown sugar and butter in 8-inch-diameter cake pan with 2-inch-high sides (preferably nonstick). Place cake pan over medium heat and whisk constantly until butter and sugar melt and mixture is smooth and bubbling. Using pot holders, remove pan from heat; cool 15 minutes. Sprinkle blueberries evenly over.

For lemon-almond butter cake:
Sift flour, baking powder, and salt into medium bowl. Combine almond paste, sugar, and lemon peel in bowl of stand mixer fitted with paddle attachment. Beat on medium speed until almond paste is broken into very small pieces, about 1 minute. Add butter, 1 piece at a time, beating until mixture is smooth and scraping down sides of bowl occasionally. Add eggs, 1 at a time, beating well and scraping sides of bowl after each addition. Add flour mixture and beat just until batter is smooth. Spoon batter in dollops over blueberries in pan; spread evenly with offset spatula to smooth.

Bake cake until deep golden and tester inserted into center comes out clean, about 43 minutes. Remove from oven; let stand 1 minute. Run small knife around cake to loosen. Place large platter atop pan. Using oven mitts or potholders and using both hands, hold platter and cake pan firmly together and invert; shake gently, allowing cake to settle on platter. Cool at least 20 minutes.

Garnish cake with lemon slices and lemon peel curls, if desired. Serve warm or at room temperature with additional blueberries and Lemon Whipped Cream.

Combine all ingredients in medium bowl. Using electric mixer, beat to soft peaks. (Can be made 4 hours ahead. Cover and chill. Rewhisk before using.)