Place the whole tomatoes in a large pan. Top with chopped onion, green peppers, red pepper, garlic, and minced meat. Cover and cook on low heat until the tomatoes soften.
Remove the tomato skins, then mash everything together in the pan. Stir in the tomato paste, salt, and pepper, mixing well.
Arrange the lasagna sheets on top of the sauce. Cover and cook until the sheets are soft and fully cooked.
Sprinkle grated cheese over the top, cover briefly to melt, then garnish with chopped parsley and serve.
Notes
Skip the vegetable oil if your minced meat is fatty enough to render its own juices.
Keyword lasagna recipe, lasagna without oven, no-bake lasagna, one-pan lasagna