Add the oil to a skillet over medium heat. Add diced onions and garlic to skillet. Cook until just tender. Remove to a bowl and set aside. Add beef to skillet and cook until completely browned, add 1/2 pack of taco seasoning and cook for another 2 minutes. Remove from heat and drain away any drippings. Add onions and garlic back to beef and stir to combine. Pour the can of enchilada sauce into the beef and continue cooking for 2-3 minutes.
Transfer the enchilada mixture from the skillet into a 9-by-13-inch baking dish. Scatter the tater tots on top. sprinkle the cheese and top with black olives.Bake uncovered for 15-20 minutes or until the cheese is bubbly and tater tots are golden brown. Garnish with scallions or cilantro for added color. Serve warm while the cheese is gooey!