Vegetarian lentil and chickpea burgers with tahini sauce

Ingredients

• Vegetarian lentil and chickpea burgers
• 1 tablespoon vegetable oil
• 1 onion, finely chopped
• 2 garlic cloves, crushed
• 400 grams can brown lentils, drained, rinsed
• 400 grams can chickpeas, drained, rinsed
• 1 cup cooked long-grain brown rice
• 1/4 cup sun-dried tomato pesto
• 1/4 cup plain flour
• 4 hamburger buns, split in half
• 50 grams baby spinach leaves
• 1 carrot, cut into ribbons
• 8 slices drained canned beetroot
• sumac to sprinkle
• Tahini sauce
• 1/2 cup extra-light sour cream
• 2 tablespoons tahini
• 2 tablespoons warm water