Steam tempeh: Use a steamer basket to steam the cubed tempeh for 10 minutes. If you don't have a steamer basket, fit a metal colander/sieve into a medium pot filled with simmering water. The sieve should not touch the water. Cover tightly with the pot lid.
In a medium bowl, toss the steamed tempeh with the soy sauce, nutritional yeast, olive oil, onion powder, garlic powder, and black pepper.
Transfer to a half sheet pan. Spread out so that there is about an inch between each piece of tempeh.
Bake at 350F for 12 minutes on the middle oven rack. After 12 minutes, remove from the oven and stir. Return to the oven for 10-12 minutes, until the tempeh is golden.
Remove from the oven and enjoy.
Notes
Steaming tempeh: You can technically skip this step but I recommend it because it removes the bitter flavor that some people find offputting. It also helps the tempeh absorb flavor.
Leftovers: Enjoy within 3-4 days. Keep refrigerated in a closed container. This tempeh freezes well for up to 3 months.