How to Make It
Preheat oven to 425°F. Toss pepitas with 1 teaspoon of the oil, ¼ teaspoon of the salt, and several grinds pepper on a rimmed baking sheet. Rub potatoes with remaining 3 tablespoons oil and place cut side down on a second rimmed baking sheet. Add a few grinds of pepper. Transfer both baking sheets to oven.
Bake pepitas until golden, 5 to 6 minutes. Remove from oven. Continue baking potatoes until very tender, 22 to 28 minutes more. Let cool slightly, about 5 minutes, then scoop potato flesh into a large bowl. Return potato skins to baking sheet.
Increase oven temperature to broil and position top rack 6 inches from heat. Broil potato skins until crispy, 1 to 2 minutes.
Add black beans, a few grinds pepper, 1 cup of the cheese, and remaining 1 teaspoon salt to sweet potato flesh and stir to combine. Divide mixture among skins and top with remaining ½ cup cheese. Return to oven and broil until cheese is melted, 2 to 3 minutes. Top with avocado and pepitas.