Cut the tomatoes into small cubes. Halve the avocado, remove the pulp and cut it into small cubes. Peel the onion, cut in half and cut into fine cubes. Finely chop the coriander.
Mix the olive oil, vinegar, salt and pepper with a small whisk until everything has combined.
Then mix everything in a nice bowl. Let the salad rest for about an hour and then serve.