There are many variations on the traditional marinière sauce. This is the simplest. From this point on you can add some hot red pepper to give a spicy sauce, or black pepper, herbs, a pinch of flour in order to bind the sauce, etc.
Submerge the clams in plenty of water and leave them for some time to eliminate any sand.
Meanwhile, peel the garlic cloves and chop finely.
Heat a little olive oil in a pan and add the garlic. When it begins to turn golden, add the grated tomato and allow to cook for some time until the mixture becomes well concentrated.
Then pour over some white wine, allow to reduce for a few seconds and add the clams. Cover and cook until they open.
This will only require a minute. Then sprinkle with chopped parsley and serve.