Preheat a skillet over medium-high heat. Add the olive oil and corn kernels. Cook for 3-4 minutes, stirring occasionally, until the corn is charred and slightly caramelized. Set aside.

In the same skillet, add the black beans, smoked paprika, ground cumin, and a pinch of salt and pepper. Cook for 2-3 minutes until warmed through and slightly seasoned. Remove from heat.

Prepare the avocado crema: In a blender or food processor, combine the avocado, sour cream or Greek yogurt, lime juice, garlic powder, and a pinch of salt. Blend until smooth and creamy. Adjust seasoning if needed.

Assemble the tostadas: Spread a layer of the avocado crema evenly over each tostada. Top with the black beans and charred corn.

Garnish with crumbled queso fresco or feta cheese, chopped cilantro, and sliced jalapeño (if using). Serve with lime wedges on the side for squeezing over the tostadas.