Cook beef and garlic powder in a skillet, stirring until crumbled and no longer pink. Remove from heat; drain. Stir in shredded cheese and onion; set aside.
Heat next 3 ingredients in a saucepan over medium heat; stir until melted. Stir in dip mix, chiles, and pimiento.
Pour water to a depth of 1 inch in a skillet; heat over medium-high heat. Dip tortillas, 1 at a time, into hot water, using tongs; soak 2 to 3 seconds. Spoon about 1/3 cup meat mixture onto 1 side of each tortilla; roll up tightly, and place in a lightly greased 13- x 9-inch baking dish. Top with cheese sauce.
Bake, covered, at 350° for 30 minutes. Uncover and bake 10 more minutes.