Preheat your oven to 400°F (200°C) and line a baking sheet with parchment paper for easy cleanup.
Slice the tempeh block into 1/2-inch thick strips or triangles to maximize the surface area for the marinade.
In a small mixing bowl, whisk together the tamari, lemon juice, lemon zest, olive oil, dried oregano, garlic powder, sea salt, and black pepper.
Place the tempeh pieces in a shallow dish and pour the marinade over them, turning each piece to ensure it is thoroughly coated; let marinate for at least 10 minutes.
Arrange the marinated tempeh in a single layer on the prepared baking sheet and bake for 20-25 minutes, flipping halfway through, until the edges are crispy and golden brown.
While the tempeh is baking, steam the broccoli florets until they are tender-crisp and vibrant green, and gently reheat the pre-cooked quinoa.
Assemble the meal by placing the fluffy quinoa in a bowl, topping it with the baked tempeh slabs, and serving the steamed broccoli on the side.