Cook ground beef and farro and set aside.
Preheat your oven to 375°F.
Scoop out the flesh from the eggplant halves, leaving about a 1/4-inch border around the edges. Chop the scooped-out flesh and set aside. Place the eggplant halves on a baking sheet, brush with a tablespoon of olive oil, and sprinkle with salt. Bake for 20 minutes or until slightly softened.
In a large skillet, heat the remaining half tablespoon of olive oil over medium heat. Add the onion and sauté for 3-4 minutes until translucent. Add the garlic and cook for another minute until fragrant.
Add the chopped eggplant flesh, bell pepper, and zucchini. Sauté for about 5-7 minutes, until the vegetables are tender.
Stir in the cherry tomatoes, cooked farro, oregano, basil, red pepper flakes (if using), salt, and pepper. Cook for an additional 2-3 minutes until everything is well combined.
Remove the eggplant halves from the oven. Spoon the vegetable mixture evenly into the eggplant shells, pressing down gently to pack it in.
Return the stuffed eggplants to the oven and bake for another 15-20 minutes, until the eggplant is tender and the filling is heated through.
Remove from the oven and sprinkle with crumbled feta cheese.