Melt 1 tablespoon butter in a skillet over medium-high heat. Add onion and shallots; saute 5 minutes or until tender. Cool and set aside.
Combine cornmeal and next 5 ingredients in a bowl. Set aside.
Whisk together 1/2 cup butter, buttermilk, and eggs in a separate bowl. Stir in onion mixture, cheese, and roasted pepper.
Add cheese mixture to cornmeal mixture, stirring just until dry ingredients are moistened. Pour into a greased 13- x 9-inch pan. Bake at 400° for 30 minutes or until a wooden pick inserted in center comes out clean. Cool on wire rack.