Preheat the Oven: Set the oven to 450°F and lightly grease a rimmed baking sheet with olive oil.
Prepare the Tofu: Cut the tofu into ¾-inch-thick slices and pat them dry thoroughly using paper towels. Arrange the slices in a single layer on the greased baking sheet.
Make the Sauce: In a small mixing bowl, combine half the grated garlic with the fish sauce, lemon juice, and ¼ cup of olive oil. Season both sides of the tofu slices with salt, then use a brush to coat them with half of the sauce mixture. Transfer the baking sheet to the oven and roast for 20 minutes.
Prep the Broccoli Rabe: While the tofu cooks, prepare the broccoli rabe. Use a mortar and pestle or the side of a knife blade to gently crush the coriander seeds, if using (there’s no need to grind them fully). Toss the broccoli rabe in a large bowl with the remaining grated garlic, crushed coriander seeds, the remaining ¼ cup of olive oil, ½ teaspoon of salt, and the chile flakes if desired.
Roast the Broccoli Rabe: Spread the broccoli rabe evenly on a separate baking sheet. Add it to the oven alongside the tofu and roast, stirring once or twice, until the rabe is tender and golden at the edges. This should take about 10 to 13 minutes.
Flip and Finish the Tofu: Turn the tofu slices over and brush them with the remaining sauce mixture. Continue roasting until the underside turns golden brown, approximately 5 to 10 more minutes.
Assemble the Dish: Once cooked, toss the warm broccoli rabe with the grated lemon zest and a drizzle of olive oil. Serve the broccoli rabe layered over the tofu slices for a complete and flavorful meal.