Slice spaghetti squash in half and scoop out seeds. Lay cut side down in baking pan with water and bake 400 degrees for 30-40 minutes until fork tender. Allow to cool.
While squash is cooling, cook meat fully and drain if greasy.
Scoop the spaghetti squash out and mix in a bowl with meat, sauce, salt and pepper. Split mixture and add back to squash shells. Top with tomatoes, peas and cheese.
Bake 400 degrees for 25-30 minutes uncovered until cheese melts and is bubbling.
Spaghetti squash can be cooked and scooped ahead of time. Refrigerate up to five days until ready to cook.