Preheat oven to 400°F (200°C). Wash, scrub, and pierce sweet potatoes. Bake 45–55 min until tender.
Heat oil in skillet. Sauté garlic 1 min. Add bell pepper, cook 3–4 min. Stir in beans, corn, lemon juice, salt, and pepper. Cook 3–5 min.
Mash avocado with salt and lemon juice, or slice for topping.
Cool potatoes slightly. Slice lengthwise, press ends to open, fluff insides.
Fill with bean-corn mix. Top with cheese to melt.
Add avocado, herbs, and extra lemon. Serve warm.