01 - Combine ground turkey, chopped onion, minced garlic, parsley, smoked paprika, cumin, salt, and black pepper in a bowl. Mix gently until just combined.
02 - Shape the mixture into four equal-sized patties.
03 - Heat olive oil in a skillet or grill pan over medium heat. Cook patties 5 to 6 minutes per side until golden brown and fully cooked (internal temperature 165°F). Remove and let rest.
04 - In a bowl, mash avocados until mostly smooth. Stir in diced tomato, red onion, jalapeño if using, cilantro, lime juice, salt, and pepper. Adjust seasoning as needed.
05 - Optionally, lightly toast the burger buns.
06 - Layer lettuce on the bottom bun, add a turkey patty, spoon guacamole over it, then top with sliced tomato and red onion. Cover with the top bun.
07 - Serve the assembled burgers fresh for best flavor.