Set oven rack about 6 inches from the heat source and preheat the oven's broiler.
Lay crackers salt side down on a baking sheet. Spread tomato paste on top.
Microwave sausages in a microwave-safe plate until heated through, about 1 minute. Slice in half lengthwise, making sure not to cut all the way through. Place sliced side-down onto the crackers. Quarter each slice of cheese and lay over the sausage.
The cheese is optional and replaceable. My family always used American due to it always being in the fridge. Substitute the paste for pizza sauce, the crackers for whole wheat or low sodium, or the sausage for pepperoni. They're your pizzas, so make them how you want!