Preheat oven to 350 degrees. Combine flour and powdered sugar. Sift mixture into a medium bowl; repeat procedure. Whisk in 1/4 cup granulated sugar; set aside.
Beat egg whites in a large bowl at high speed with an electric mixer until foamy. Add cream or tartar and salt, beating until soft peaks form. Gradually add remaining 3/4 cup sugar, 2 Tbsp. at a time, beating until stiff peaks form and sugar dissolves. Add vanilla, lemon juice, and almond extract, beating until blended. Sprinkle flour mixture over egg white mixture, 1/4 cup at a time, gently folding in after each addition.
Using 2 (24-cup) mini muffin pans lined with mini paper baking cups, coat with cooking spray and fill each cup two-thirds full. Bake for 10 minutes or until a wooden pick inserted in center comes out clean. Cool in pans on wire racks 10 minutes; remove from pans to wire racks, and cool completely.
To prepare frosting, beat cream at high speed with an electric mixer until stiff peaks form. Beat mascarpone, powdered sugar, vanilla, and salt in a large bowl at medium speed with mixer until blended. Gently fold whipped cream into mascarpone mixture until blended. Makes 3 cups.
Insert metal tip no. 21 into a large decorating bag; fill with frosting. Pipe a small circle of frosting in the center of each cupcake. Top each with an edible flower blossom. You may prefer to remove the flower before eating the cupcake.