Start by cooking the sweet potato fries according to the package instructions or make your own homemade version.
Heat a skillet over medium heat. Add the avocado or olive oil and sauté the chopped onion for 3-4 minutes until softened and aromatic.
Add the ground beef, turkey, or chicken along with mustard, garlic powder, onion powder, salt, and black pepper. Cook until browned and cooked through, breaking it up as it cooks (7-8 minutes).
In a small bowl, combine plain Greek yogurt, mayonnaise, ketchup, mustard, pickle juice, finely chopped pickles, garlic powder, onion powder, and salt. Stir until smooth and creamy. Taste and adjust seasoning if desired.
Divide the shredded lettuce evenly among four bowls. Top with the cooked ground meat, diced tomatoes, red onion, chopped dill pickles, and avocado slices (optional).
Serve each bowl with a side of crispy sweet potato fries and drizzle generously with the homemade Big Mac sauce.