You know that huge container of grapes that looked so good at the grocery store but is now taking up space in the fridge after you realized one human could never eat that many grapes? This is a crazy delicious way to use them. AND it goes over great at potlucks! Major potluck winner, everyone will ask you where you came up with it. Go ahead, take the credit.
Combine red grapes, green grapes, black grapes, roma tomatoes, onion, serrano chile pepper, garlic, cinnamon, cloves, salt, and black pepper in a large bowl. Cover and refrigerate for 3 hours before serving.