Slice the tempeh into 12 strips, place in a steamer basket, and set over a pot with 1-inch of water. Bring the water to a simmer, cover, and let steam for 10 minutes.

Preheat the oven to 425°F and line a baking sheet with parchment paper.

In a small bowl, whisk together the hoisin sauce, sriracha, ginger, and lime zest. Reserve half of the sauce for serving and toss the remaining half with the tempeh and set aside for 20 minutes to marinate. Place the tempeh on the baking sheet and bake for 10 to 12 minutes or until browned around the edges.

Squeeze a little lime juice over the avocado, cucumber, and carrot.

Heat the bao buns according to package directions and assemble each with the tempeh, spooning a little sauce over each tempeh piece, the avocado, veggies, herbs, and chiles. Serve with remaining sauce on the side and lime slices for squeezing.