Heat oven to 350°F. Spray 9x2-inch round baking pan with cooking spray. Line bottom with parchment paper; spray paper. Dust with flour, tapping out excess. Whisk flour, baking powder and 1/2 teaspoon salt in medium bowl.
Beat almond paste in large bowl at medium to medium-high speed 1 to 2 minutes or until crumbled. Add butter and 3/4 cup sugar; beat at medium speed 2 minutes or until smooth and creamy.
Add eggs one at a time, beating well after each addition. Beat in vanilla and 1/2 teaspoon almond extract. At low speed, beat in flour mixture just until combined. Increase speed to medium; beat 30 seconds. Spread in pan; top with rhubarb.
Bake 55 to 60 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack 10 minutes; invert cake onto wire rack. Remove parchment paper; turn cake top-side up. Cool completely.
Meanwhile, coat baking sheet with cooking spray. Whisk egg white in small bowl until frothy. Stir in remaining almond crunch ingredients; spread on baking sheet. Bake 10 minutes or until golden brown, stirring once. Cool completely on wire rack.
Whisk powdered sugar, 2 tablespoons cream and 1/4 teaspoon almond extract in small bowl until smooth, adding additional cream 1/2 teaspoon at a time to desired glaze consistency.
Drizzle glaze over top and sides of cake; top with almond crunch. Let stand until glaze is set.