Meanwhile, we put a teaspoon of vegetable oil in a nine by thirteen inch glass baking dish. We peel and dice the onion—yielding roughly one cup—and add it to the baking dish. We put the baking dish in the oven.
While the onion cooks, we carefully slice the carrots. After the onion has been cooking for 5 minutes, we add the pre-sliced mushrooms to the baking dish and stir with a heat-safe spatula. Five minutes later, the carrots are added—about 1 cup. We let the vegetable mixture cook for 10 minutes while we prepare the sauce.
Meanwhile, the ginger is peeled and minced, yielding 2 teaspoons. The garlic is also peeled and minced, yielding a heaping tablespoon. In a bowl, we combine the ginger and garlic with the rest of the vegetable oil, the soy sauce and the sesame oil.
About 10 minutes after we added the carrots to the oven, we take the pan out of the oven. We lay the tilapia fillets on top of the vegetables and pour on the sauce. We cover the baking dish (careful, it’s hot!) with some aluminum foil and put it back in the oven. It is baked for about 15 minutes until the fish is cooked through.
We serve the tilapia, vegetables, and sauce over rice. To brighten up the plate, we sprinkle with the fresh herbs and a squeeze of lemon.