In a large skillet, heat olive oil over medium heat.

Add the sliced onion and cook, stirring occasionally, for about 15-20 minutes until the onions are caramelized and golden brown. Remove from heat and let cool slightly.

In a mixing bowl, combine mayonnaise, Dijon mustard, lemon juice, and the cooled caramelized onions. Season with salt and pepper to taste. Set aside.

In the same skillet, cook the ground beef over medium-high heat, breaking it apart with a spatula. Season with garlic powder, onion powder, salt, and pepper. Cook until browned and cooked through, about 7-10 minutes.

To assemble the bowls, divide the cooked quinoa among four bowls. Top each with cooked ground beef, cherry tomatoes, shredded lettuce, avocado slices, and shredded cheddar cheese.

Drizzle generously with the caramelized onion aioli.

Serve immediately and enjoy!