Heat the oil in a large nonstick skillet to medium-high; add garlic and onion, and sautée until onion is just tender, about 3-4 minutes. Add the tempeh and sautée for 3-4 minutes. Season onion and tempeh with salt to taste. Mix in the paprika, cayenne pepper, cumin, and corn kernels.
In a small bowl, whisk together the marinara sauce and green chiles. Pour the marinara–green chile mixture into the skillet with the tempeh; mix well to combine. Stir in the cilantro and black beans.
Stuff the peppers with the tempeh mixture. Arrange the peppers in a 5- or 6-quart slow cooker. Cover and cook the peppers on high for 2 hours or on low for 4 hours.
Remove the lid and top the peppers with the shredded cheese, replace the cover, and cook on high for 15-20 additional minutes. Allow peppers to cool 10-15 minutes before serving. Serve warm.
Source: Whole Foods Diet Cookbook