Heat oven to 375°F. Pour enchilada sauce into a bowl and whisk in your favorite BBQ sauce until combined. Stir in cayenne pepper and taco seasoning.
In a large skillet, heat 2 tablespoons of olive oil on low-medium. Add sliced onions with a pinch of salt, and let caramelize until soft and golden – about 10 minutes. Remove onions from pan. Add chicken and cook until brown on each side and cooked through, about 5 minutes. Add 1/2 the sauce to the pan and stir until covered.
Spray a 9-inch round pan with canola and place one tortilla on the bottom. Brush with sauce and top with 1/3 chicken mixture. Sprinkle with cheese and top with another.
Pour a drizzle of enchilada/BBQ sauce in the bottom of a baking dish. Take each tortilla and fill it with 1/2 + of chicken mixture. Top with another and repeat 2 times. Sprinkle cheese over the top and bake for 15 minutes or until top is lightly brown. Serve with salsa and sour cream.