Microwave frozen cauliflower florets in a microwave-safe bowl for 3-5 minutes (or follow instructions on packaging). Once done and slightly cooled, make sure to drain any excess water.
Using the ricer attachment or grating attachment of the food processor, rice the cauliflower. Working in batches, lay the grated cauliflower out onto a dish towel, and squeeze excess water from the cauliflower. Set aside.
Heat oil in a large skillet over medium-low heat.
Add the onion, and cook, stirring often, until it begins to become tender, about 5-8 minutes.
Add the garlic, and cook for an additional 2-3 minutes.
Add the salt, chili powder, ground cumin, and ground paprika to the pan, stirring to release the aromatics of the spices. Add the tomatoes, and cook for about 2-3 minutes, until they begin to soften.
Once the tomatoes are softened, add the cauliflower rice, and cook, stirring occasionally, 10-12 minutes, or until the “rice” is tender and lightly browned.
Remove from the heat and stir in the cilantro. Serve with lime, if desired.