4-6 medium (2 lbs) tomatoes
4-5 small (1 lb) cucumbers, or 1 english cucumber)
1 small onion, thinly sliced (~1/4 lb)
2 Tbsp Sunflower or Extra virgin olive oil (Ellen's comment, for this, I like sunflower better)
1 Tbsp distilled white vinegar (I do like champagne or white wine vinegar here)
1 tsp fine sea salt, or ¾ tsp table salt
¼ tsp Pepper to taste
2 Tbsp Green onion for garnish (optional)