1Heat oven to 375°F. Line 8-inch square pan with foil; spray foil with cooking spray. In 2-quart saucepan, heat butter over medium-high heat about 5 minutes, stirring frequently, until a rich hazelnut-brown color. Remove from heat; cool 5 minutes.
2Meanwhile, in food processor, place slivered almonds. Cover; process until finely ground. In large bowl, stir together ground almonds, powdered sugar, flour and salt. Add vanilla, almond extract and egg whites; beat about 1 minute or until blended.
3Add browned butter; beat on medium speed until smooth, about 1 minute. Pour batter into pan. Sprinkle sliced almonds evenly over top; sprinkle with sugar crystals.
4Bake 20 to 25 minutes or until golden brown. Cool completely in pan on cooling rack, about 1 hour. Using foil, lift cake from pan; remove foil from cake. Cut into 6 rows by 4 rows.