Position an oven rack in the center and preheat the oven to 425°F (220°C). Line a rimmed baking sheet with parchment paper.
Scrub the sweet potatoes under cool running water, dry them completely, and pierce each 6 to 8 times with a fork. Rub with olive oil and sprinkle with kosher salt, then place on the prepared baking sheet with space between each one.
Bake for 45 to 55 minutes, rotating the sheet once halfway through, until the skins are blistered and a knife slides to the center with no resistance. The center should read about 205°F (96°C).
When the potatoes have about 15 minutes left, heat 1 tablespoon olive oil in a 12-inch skillet over medium heat. Add the diced onion and cook for 4 to 5 minutes until soft and translucent.
Stir in the minced garlic and cook for 30 seconds until fragrant. Add the chili powder, ground cumin, and smoked paprika, stirring constantly for about 1 minute to toast the spices.
Add the drained black beans, 1/2 cup salsa, 1/2 teaspoon kosher salt, and 1/4 teaspoon black pepper. Stir to coat, then reduce heat to medium-low and simmer for 4 to 5 minutes until thickened.
Mash roughly one quarter of the beans against the pan with the back of a spoon to give the filling body. Remove from heat and stir in 1 tablespoon lime juice. Taste and adjust salt if needed.
Remove the baked potatoes from the oven and let them rest for 5 minutes. Leave the oven on at 425°F (220°C). Cut a lengthwise slit along the top of each potato, going about three quarters of the way through.
Press the ends of each potato toward the center to open the slit into a boat shape, then use a fork to fluff the exposed flesh into soft, loose strands.
Spoon about 2/3 cup of the black bean filling into each potato, mounding it generously in the center. Sprinkle 1/4 cup shredded Monterey Jack over each potato.
Return the baking sheet to the oven and bake for 8 to 10 minutes, until the cheese is fully melted, bubbling at the edges, and just starting to brown in spots.
Top each hot potato with 2 tablespoons Greek yogurt, fan out sliced avocado over each one, spoon 1 tablespoon salsa on top, and sprinkle with 1 1/2 teaspoons chopped cilantro. Serve immediately.