Preheat the oven to 400°F and line a couple of baking sheets with parchment paper.
Place the tofu, cornstarch, 1 tablespoon of the olive oil, soy sauce, cumin, coriander, garlic powder, cayenne pepper, and salt into a large bowl. Toss the ingredients well to coat the tofu in the seasonings.
Arrange the tofu cubes on a baking sheet and bake for 30 minutes. Keep the bowl handy, as you'll use it later.
Cook the rice while the tofu bakes. Combine the basmati rice, water, olive oil, turmeric, and salt in a medium saucepan and place it over high heat. Bring the liquid to a boil, then reduce the heat to a low simmer and let the rice cook, covered, for about 20 minutes, until all of the liquid has been absorbed. Let the pot sit with the lid on for 10 minutes when the rice has finished cooking.
While the rice cooks and the tofu bakes, arrange the vegetables in a single layer on a baking sheet. Drizzle them with olive oil, then rub it evenly into the veggies with your hands. Place the baking sheet into the oven with the tofu and roast the vegetables for about 20 minutes, until tender and browned in spots. Season them with salt and pepper to taste when they come out of the oven.
When the tofu has just a few minutes left to bake, stir the remaining 2 tablespoons of olive oil together with the tomato paste. After the tofu has baked for 30 minutes, remove the baking sheet from the oven and carefully transfer the tofu back to the bowl. Toss it with the tomato paste mixture, using a spoon to stir it up (it will be hot, so avoid using hands).
Arrange the tofu in an even layer on the baking sheet and return it to the oven for about 10 minutes, until crispy and very dark. Keep a close eye on it during this final baking stage, as it can burn fast.
After the rice has sat covered for 10 minutes, remove the lid and fluff it with a fork. Stir in the lemon juice and zest, and season it with additional salt, if desired.
Whisk the dressing ingredients together in a small bowl, thinning the mixture with as much water as is needed to achieve a creamy but pourable consistency. Season with additional salt to taste, if desired.
Divide the rice, vegetables, tofu, and olives onto plates or among bowls. Top each serving with a drizzle of the dressing and a sprinkle of fresh cilantro and scallions. Serve.