You'll need:
1/4 cup red onion, diced
1/2 a pint of cherry or grape tomatoes, sliced in half (*see note)
1/2 a cucumber, quartered and sliced
1/2 a ripe avocado, chopped
Juice of 1/2 a lime
Olive oil
Salt and pepper, to taste
Combine the onion, tomatoes, and cucumber in a bowl. Toss the avocado with the lime juice and add to the salad. Season to taste, and drizzle some olive oil over all. Enjoy!
*Note: an easy way to cut cherry or grape tomatoes in half is to lay them on an overturned plate, place another plate right side up on top of them, and run a sharp knife carefully through all.