Bring vegetable broth to a boil in a small pot. Add the rice, turmeric, and salt. Give it a stir, cover, and set the heat to low. Cook until the rice is tender, about 15 minutes (time will vary depending on the type of rice you're using, so check the instructions on the package). When done, remove from heat and keep covered until ready to serve.
While the rice cooks, heat olive oil in a large saucepan over medium-high heat. Add the sliced green chili peppers, cumin, and chili powder. Stir and simmer until the peppers are tender—about 2-3 minutes.
Drain the mackerel of its oil and add it to the pan with the green chili. Give it a toss to break the mackerel apart and warm it through. When done, remove from heat and set aside.
Combine the tomatoes and scallions in a small bowl. Squeeze the lime juice from half of the lime over the bowl and stir to mix; set aside. Cut the other half of the lime into four small wedges for serving.
Fluff the rice with a fork and add 1 TBSP of butter; mix in well. Place some of the rice into a bowl, and save the rest for another meal or Mexican rice bowls throughout the week! Top with the mackerel and peppers, and then with the tomato and scallion blend. Finish the bowl off with a dollop of sour cream, some fresh chopped herbs, and a lime wedge for an extra squeeze of fresh lime juice :)