Begin by preheating your oven to 375°F (190°C). In a large bowl, combine the shredded russet potatoes, melted butter, garlic powder, salt, and pepper. Press this mixture firmly into the base of a greased baking dish, creating a compact layer for the foundation of your casserole.
In a skillet over medium heat, brown the ground beef, ensuring it's cooked through. Add the diced onion and red bell pepper, sautéing until softened. Introduce the black beans, corn, and diced tomatoes, letting the flavors meld together for a harmonious blend.
In a separate bowl, whisk together the sour cream, mayonnaise, ground cumin, chili powder, salt, and pepper. This luscious sauce will be the soul of your Tex-Mex creation, infusing each bite with a creamy, tangy allure.
Layer the Tex-Mex filling evenly over the hashbrown base, ensuring every inch is embraced by the savory medley. Pour the Creamy Tex-Mex Sauce generously, letting it cascade over the ingredients, promising a rich and indulgent experience.
Sprinkle the shredded cheddar cheese over the casserole, creating a golden crust that beckons with gooey goodness. For those craving an extra punch, strategically place sliced jalapeños on top. Your culinary canvas is nearly complete.
Bake the Tex-Mex Hashbrown Casserole in the preheated oven for 30-35 minutes or until the cheese is bubbly and golden. As the aroma wafts through your kitchen, you'll know a masterpiece is in the making.