Preheat the oven to 350 degrees. Spray a 9 x 13-inch casserole dish or two smaller 8-inch dishes.
After ground beef has browned, stir in the water, taco seasoning, onion, and pepper. Let simmer for a few minutes or until onion and pepper are almost tender.
In a small bowl, mix together the Bisquick and water. Once it becomes a soft dough, press it into the casserole dish. Set aside.
In another small bowl, combine the mayo, sour cream, Rotel, and 1 cup of the cheese.
Spread the beef mixture onto the dough, then evenly layer over it the cheese mixture. Sprinkle the remaining cup of cheese on top.
Cover with foil and freeze or leave uncovered and bake for 25-30 minutes or until cheese and edges are turning golden.