Garden tomatoes don't really need anything to taste good. But if you're wanting to dress them up a little, rough chop a few tomatoes, sprinkle with salt and pepper and drizzle with olive oil and red wine vinegar. Don't over due the oil and vinegar. It doesn't take much. You still want the tomato to be the star, not the dressing. Sprinkle with a little parsley for the finishing touch.
I don't usually use measurements for this, but if I had to give a recipe, it would probably be this....
3 good sized garden tomatoes, roughly chopped
2-3 tbs. olive oil
2-3 tbs. red wine vinegar
salt and pepper to taste
parsley for garnish
Toss everything together before serving.