In a salad bowl, pour olive oil, walnut oil, wine vinegar, salt and pepper to taste. We connect everything. Drain the water and squeeze the onion through a paper towel. Put the onion and chopped beetroot in the dressing. Stir, cover with a lid and let marinate for 30 minutes. We clean the avocado, remove the stone and cover the halves with a lemon slice so that they do not darken while we collect the salad.