Preheat oven to 400 degrees F. Line baking sheet with aluminum foil (this makes clean up easier). Scrub sweet potatoes and pat dry. Using a fork, poke holes in each one then place on baking sheet. Place in oven and bake for 45 minutes to 1 hour.
While sweet potatoes are baking, bring water to a boil then add barley, 1 tsp cumin, and thyme. Reduce heat and simmer until barley is tender and liquid absorbed about 35-45 minutes.
Alternatively: Place water, barley, 1 tsp cumin, and thyme in Instant Pot. Close lid, set to sealing, and turn on to high pressure for 35 minutes. Conduct natural pressure release or quick valve. Drain and rinse when done.
About 10 minutes before potatoes are done, heat olive oil in a pan, then add bell pepper, onion, and remaining tsp of cumin. Cook until tender.
Drain and rinse can of black beans. Combine barley, pepper, onions, and black beans in a bowl, seasoning with salt and pepper to taste.
When potatoes are done, pull out of the oven and let cool. Once cooled, cut a horizontally to open up the potato but not completely apart. Using a fork fluff the inside of the potatoes. Spoon stuffing mixture into sweet potatoes, approximately 1/2 cup per sweet potato. Top with lime, sour cream, salsa, guacamole, and or cheese, and enjoy!