Melt 1 tablespoon butter in a large skillet over medium-high heat; add onions, and sauté 15 minutes or until caramel colored. Place onions in a bowl, and set aside.
Combine all-purpose flour, salt, and pepper; dredge turkey tenderloins in flour mixture.
Melt remaining 2 tablespoons butter with oil in skillet over medium-high heat; add turkey tenderloins, and brown on all sides. Gradually stir in chicken broth and milk. Bring to a boil, and cook, stirring constantly, 1 minute or until thickened. Stir in onions. Add spinach, stirring just until wilted. Pour turkey mixture into a lightly greased 13- x 9-inch baking dish.
Bake, covered, at 350° for 30 minutes. Remove from oven, and arrange desired amount of Cranberry-Pecan Crusts over pie before serving. Serve with any remaining Cranberry-Pecan Crusts on the side.