Rinse the rice using a sieve until the water runs clear and set it to the side.
Dice half the onion and add the other half to your blender along with the tomatoes, tomato paste, half your garlic cloves, stock, salt, and cumin. Blend well!
To your pot (or rice cooker), add the olive oil and heat it up. Sauté the half onion (diced) and the remainder of your garlic cloves (pressed) along with a sliced jalapeño (if using) until they are fragrant and the onions become translucent.
Add the rinsed rice and sauté until there's a nutty smell and the rice starts turning light brown slightly.
Pour the tomato mixture from your blender in the pot and bring to a boil, covered.
Once your rice boils rapidly, turn the heat to medium low and let the rice cook, covered, for about 10-15 minutes. The time will depend on the heat of your stove and the depth and width of your pot. The rice is done when the rice appears a bit dry on top and no visible sauce remains.
Alternatively, set the rice cooker to cook mode and let the rice cook. This should take about 15 minutes, but the time will depend on your rice cooker.
Once the rice is done, remove it from the heat and let it sit covered for about 5 minutes.
Fluff the rice with a fork, optionally mixing some chopped cilantro and lime juice throughout.
Serve as a side dish or as a filling for your favourite burritos, fajitas, or wraps.