0 Heat the oven to 425°F. Rub 1 tablespoon of the oil all over the sweet potatoes, then season with 1/2 teaspoon salt and several grinds pepper. Place cut side down on a baking sheet. Roast until very tender, 25 to 35 minutes.
1 Meanwhile, cook the lentils: Bring a medium pot of salted water to a boil. Add the lentils, reduce the heat to medium-low, and simmer, uncovered, until the lentils are just tender but still have a slight bite, 12 to 15 minutes. Drain and transfer to a small bowl. Stir in the vinegar and season generously with salt to taste (these should taste good enough to eat on their own!).
2 Heat the remaining 1 tablespoon oil in a large skillet over medium heat until shimmering. Add the onion and bell pepper and cook until softened, about 3 minutes. Add the garlic, chili powder, 1 teaspoon salt, and several grinds pepper and cook, stirring, until fragrant, about 1 minute. Stir in the tomato paste and cook until darkened in color, about 2 minutes.
3 Stir in the water, cooked lentils, ketchup, soy sauce, mustard, maple syrup, and the remaining 1/2 teaspoon salt.
4 Reduce the heat to medium-low and simmer, stirring occasionally, until the mixture has thickened enough to scoop but still has “sloppy joe” vibes, about 12 minutes. Remove from the heat and season with salt and pepper to taste.
5 When the sweet potatoes are done, flip them upright and smash the flesh with a fork. Divide the sloppy joe mixture between them (reserve any extra to serve on the side, if needed). Top with the cheese.
6 Return to the oven until the cheese is melted, about 5 minutes. Serve with scallions, hot sauce, and raw or pickled jalapenos, if using.
