Combine sliced strawberries and 1/4 cup sugar in a bowl; stir well. Cover and chill 2 hours.
Preheat oven to 375°.
Line a 9-inch round cake pan with wax paper. Coat pan with cooking spray, and dust with 1 teaspoon flour; set aside.
Cream margarine at medium speed of a mixer; gradually add 1/2 cup sugar, beating until light and fluffy (about 5 minutes).
Combine 1 3/4 cups flour, baking powder, and salt; stir well. Add flour mixture to creamed mixture alternately with milk, beginning and ending with flour mixture. Stir in almond extract.
Beat egg whites and cream of tartar at high speed of a mixer until foamy. Gradually add 2 tablespoons sugar, 1 tablespoon at a time, beating until stiff peaks form. Gently stir about one-fourth of egg white mixture into batter. Gently fold in remaining egg white mixture.
Pour batter into prepared pan. Sprinkle turbinado sugar over top of cake. Bake at 375° for 25 minutes or until a wooden pick inserted in center comes out clean. Let cool in pan 10 minutes on a wire rack; remove from pan, and let cool completely on wire rack.
Slice shortcake in half horizontally. Place bottom half, cut side up, on a serving plate. Drain strawberries, reserving juice; drizzle half of juice over bottom cake layer. Spread 1 cup whipped topping over cake layer, and arrange half of strawberries over whipped topping. Top with remaining cake layer, cut side down, and drizzle with remaining reserved juice. Spread remaining cup whipped topping over top cake layer, and arrange remaining half of strawberries over whipped topping. Garnish with a mint sprig, if desired.