1. Preheat oven to 350°. Bake pecans in a single layer in a shallow pan 5 to 7 minutes or until lightly toasted and fragrant, stirring halfway through.
2. Stir together butter and next 3 ingredients in a large bowl until blended.
3. Combine flour and next 3 ingredients; add to butter mixture, stirring until blended. Stir in apples and 1 cup pecans. (Batter will be very thick, similar to a cookie dough.) Spread batter into a lightly greased 13- x 9-inch pan.
4. Bake at 350° for 45 minutes or until a wooden pick inserted in center comes out clean. Cool completely in pan on a wire rack (about 45 minutes). Spread your choice of frosting over top of cake; sprinkle with remaining 1/2 cup pecans.