This is more guideline than recipe, but salad doesn't exactly require precise measurements. This is my favourite tomato salad and I have it frequently as a meal.
Aspasia's Tomato Salad
--in-season tomatoes, heirloom if possible (I usually use one large one, 2 to 3 medium ones, or enough cherry tomatoes to fill the serving bowl)
--half a small ripe avocado, chopped
--thin slice sweet onion, chopped (about 1/8 cup)
--about 2 oz feta cheese (sheep's milk is best), crumbled
--1/2 to 3/4 tsp dried Greek oregano
--salt to taste
--extra virgin olive oil (my brand/family oil: http://www.spartanrollinghills.com)
--good bread for dipping
Cut tomatoes into chunks and place in a bowl. If using cherry tomatoes, cut in half (you want to release the juice). Add avocado and onion. Add salt and mix. Add crumbled feta. Crush oregano over all and drizzle with a healthy amount of oil. Serve salad with bread to soak up all the tasty oil and juice left after the salad is gone :)
Optional: You can also add Kalamata olives and/or sliced cucumber and bell peppers, if you wish.