See the Supply List for items you can purchase here. You will also need:
Vegetable pan spray
Preheat the oven to 325°F. Prepare angel food pan with vegetable pan spray.
In small bowl, toss grapes with 1 tablespoon flour until evenly coated.
In medium bowl, stir together remaining 2-1/2 cups flour, baking powder, thyme leaves, baking soda and salt.
In large bowl, beat butter, sugar and lemon zest with electric mixer until very light and fluffy. Add eggs one at a time, beating well after each addition. Alternately add dry ingredients with sour cream, beating until just combined. Fold in grapes. Pour into prepared pan and smooth top.
Bake 65-70 minutes or until a toothpick inserted in the center of the cake comes out clean. Cool in pan on cooling grid 15 minutes. Loosen sides of cake from pan if necessary and remove outer ring. Loosen bottom of cake from base of pan and carefully invert to remove center core. Cool completely on cooling grid. Dust with confectioners’ sugar, if desired, and garnish with additional grapes and sprigs of fresh thyme.