Cook 1 c of lentils per the directions on the bag.
Strain the water from the lentils. Add cooked lentils and 3 cloves of garlic into a blender/food processor and pulse for ~1 minute. Lentils should be partially smooth but not completely blended. Scoop blended lentils/garlic into a large mixing bowl.
Bring a pot of water to a boil. Rinse off the beets and cut off the top and bottom of each beat. Place beets in the boiling water.
Let boil for ~30 minutes, or until beets are easily punctured with a fork.
Strain the water from the beets, and peel the skin off with a vegetable peeler.
Place beets in a blender/food processor and blend for ~ 30 seconds. There should be small pieces of beets.
Add the beets to the lentils in the large mixing bowl. Next, add in the bread crumbs, lemon juice, egg, red onion, salt, dill and feta and stir all together.
Scoop out veggie burger dough and make into patties, about 3 inches in diameter.
Let the patties sit in the refrigerator for 30 minutes to 1 hour.
Heat up olive oil in a large frying pan on medium heat. When oil is hot, add veggie burgers. Cook for about 2 minutes per side, or until lightly browned.
In a small mixing bowl, combine the yogurt, lemon juice, garlic, sun dried tomato, dill and salt. Stir together until well combined.
Assembling the pita
Cut a pita in half. Stuff it with lettuce, red onion, a veggie burger, yogurt sauce, and extra feta if you wish. Place in the toaster oven for 3 minutes and serve hot.