Peel the garlic clove and onion. Chop both finely. Add the olive oil to a small saucepan and place it over medium heat until hot. Then add the chopped onion and garlic.
Stir well. Then add the canned chopped tomatoes.
Check the seasoning again and add extra pepper, salt or vinegar to taste if necessary. Then pour the sauce in a clean serving bowl or on top of a portion of fried patatas bravas potatoes.