In a medium bowl, add in your ground turkey, salt, pepper, egg, diced onion and jalapeño, minced garlic, juice from 1 lime, and feta crumbles. Combine all the ingredients with a spoon.
Divide and form turkey mixture into 6 balls. If you weigh them, each one should be around 4.2 oz.
Place a large skillet on your stovetop and adjust heat setting to medium heat. Once skillet is hot, add in some olive oil. Once oil is hot enough, place 3 turkey patties on the skillet and flatten them slightly with a spatula. Wait 5 minutes before flipping them over. Cook for another 5 minutes or until the internal temperature reaches 165°F.
Cilantro Crema
Place cilantro, juice from 1 lime, sour cream, and salt into a small food processor. Pulse until mixture looks creamy.
Assembling your Burger
Toast hamburger buns and spread a bit of cilantro crema on each bun. Add a bed of lettuce over the bottom bun followed by a turkey patty. Spread a little (or a lot) of the cilantro crema over the patty.
Cut an avocado in half, remove the pit and scoop out the flesh with a spoon. Cut into slices and place over the patty and crema. Add a few yellow onion rings over the avocado and lastly, place hamburger bun over the onions. Serve with fries and a small side salad!