Avocado + Heirloom Tomato Salad

• 4 ripe avocados
• 3 large punnets of heirloom tomatoes
• 0.5 red onion
• 10 cup mixed leafy greens.
• 0.25 cup extra virgin olive oil
• 2 tbsp balsamic vinegar
• 1 tbsp honey
• 1 tsp dijon mustard
• 1 tsp salt