The brown mustard seeds, cumin seeds and garlic are the dominant spice flavors in this dish. I cook the celery in with the onion to use it like a spice. The pat of butter isn't necessary, but makes the dish just a little bit richer. For variation, you could add other vegetables like bell peppers or grated carrot.
Cook the short grain rice as usual with turmeric added, or use leftover rice.
While the rice is cooking, heat the oil and butter in a skillet on a medium flame. When the butter is thoroughly melted, add the brown mustard and cumin seeds and cover. When the mustard seeds start to pop and spatter, add the garlic, cover again and let cook another minute. Add onion and celery, stir and cook until onion starts to turn transparent. Add the zucchini, stir, and cook until zucchini is desired softness.
Add diced tomatoes, stir, and heat until thoroughly hot. Stir in the cooked rice and cook for 3 minutes to blend flavors. (If using leftover cold rice, heat until thoroughly hot, stirring occasionally.)
You can serve immediately, or keep in a covered dish in a 200 degree oven until ready to serve.