Preheat your oven to 400°F (200°C).
In a large, 10-inch oven-safe skillet, heat the avocado oil over medium-high heat. Add the chopped red onion and green bell pepper. Sauté for 3-4 minutes until they begin to soften.
Add the lean ground beef to the skillet. Cook, crumbling the meat with a spoon, until it is browned throughout. Carefully drain any and all excess fat from the pan.
Stir in the minced garlic and all the seasonings: chili powder, cumin, onion powder, oregano, ground coriander, and kosher salt. Cook for 1 minute more until fragrant.
Reduce the heat to medium. Add the drained black beans, tomato sauce, corn, and ground flaxseed. Stir well to combine and bring the mixture to a gentle simmer.
Scatter the pickled jalapeños evenly over the surface, followed by an even layer of the shredded Mexican cheese blend. Transfer the skillet to the preheated oven and bake, uncovered, for 15 minutes, or until the cheese is melted, bubbly, and golden brown at the edges. Serve hot.