Begin by heating the olive oil in a large skillet over medium heat.
Add the chopped onion and red bell pepper to the skillet. Sauté for about 5 minutes, or until they become soft and fragrant.
Stir in the minced garlic, chili powder, cumin, salt, smoked paprika, dried oregano, and cayenne pepper. Cook for an additional minute, allowing the spices to bloom.
Add the black beans and the drained tomatoes with green chilies to the skillet. Stir well to combine, cooking for about 2-3 minutes.
Carefully fold in the thawed and drained spinach, ensuring it is evenly distributed throughout the mixture.
In a mixing bowl, combine the mayonnaise, softened cream cheese, 1/2 cup of the sharp cheddar cheese, 1/2 cup of the Pepper Jack cheese, and sour cream. Stir until smooth and creamy.
Add the creamy mixture to the skillet, stirring thoroughly to combine all ingredients.
Sprinkle the remaining cheddar and Pepper Jack cheese on top of the dip.
Preheat your oven to 350°F (175°C). Transfer the skillet or pour the mixture into an oven-safe dish and bake for about 20-25 minutes, or until the cheese is bubbly and golden.
Remove from the oven and let it cool slightly before serving. Pair with tortilla chips, fresh veggies, or warm tortillas for the ultimate dipping experience.