Press the 14 oz block of extra-firm tofu for 20–30 minutes to remove excess moisture, then cut into about 3/4-inch cubes.
In a medium bowl, whisk together 1/4 cup tamari, 1 Tbsp rice vinegar, 1 Tbsp pure maple syrup, 1/2 tsp garlic powder, and 1/2 tsp onion powder until combined.
Add the tofu cubes to the marinade and gently toss with a spatula to coat. Let the tofu marinate 10–15 minutes, stirring occasionally for even absorption.
Preheat the oven to 375°F (190°C) and line a rimmed baking sheet with parchment paper or a silicone baking mat.
Arrange the marinated tofu in a single, spaced layer on the prepared baking sheet. Spoon any remaining marinade over the tofu if desired.
Bake for 25–30 minutes, tossing or flipping the cubes halfway through, until the edges are golden brown.
Remove from the oven and serve immediately, garnished with sesame seeds, sliced green onion, chives, and/or red pepper flakes as desired.