Preheat oven to 425°. Melt butter in a small skillet over medium heat. Add apple and next 2 ingredients; sauté 6 minutes or until onion is tender.
Combine baking mix and next 3 ingredients in a large bowl; make a well in center of mixture. Whisk together milk and eggs; add to dry ingredients, stirring just until moistened.
Stir apple mixture into batter. Spoon batter into a greased muffin pan, filling two-thirds full. Sprinkle batter with chopped pecans.
Bake at 425° for 14 minutes or until golden and a wooden pick inserted in center comes out with a few moist crumbs. Let cool in pan on a wire rack 5 minutes. Gently run a knife around edges of muffins to loosen. Remove muffins from pan to wire rack, and let cool 10 minutes. Serve warm.