Steam (Optional): Prepare a steamer basket on the stove. Cut tempeh into thin rectangular tenders. Place tempeh in a single layer in the basket, cover, and steam for 10 minutes. This is optional, but helps to remove the bitter flavor of tempeh!
Marinate: Place tempeh in a deep dish and cover with buffalo sauce, tossing to evenly coat. Let marinate at least 1 hour (or up to 12) in the fridge.
Prep: Preheat oven to 375 °F (190°C). Shake excess sauce from the tempeh and set on a plate, reserving the buffalo sauce marinade. Combine flour, salt, and pepper in one bowl, egg in another bowl, and panko in the last bowl, with a parchment-lined baking sheet at the end.
Bread: Coat each tempeh tender lightly in flour, then egg, then bread crumbs, and set on the baking sheet.
Bake: Bake for 15 minutes, flipping halfway through, until golden brown. Brush each tender with remaining buffalo sauce, then return to the oven for 5 minutes, until slightly dry.
Notes
*Make this recipe vegan by using flax egg. Combine 1 Tbsp flax seed meal and 2.5 Tbsp water. Let thicken for 10 minutes then use in place of the egg.