Run cold water through the basmati in a strainer, agitating the grains gently, then drain thoroughly. Clear runoff signals that much of the loose surface starch has washed away.
Over medium heat, warm the rice portion of olive oil in a large skillet or saucepan and soften the garlic with the optional onion for 2 to 3 minutes. Look for translucent onion and a fragrant, rather than browned, garlic aroma.
Stir the drained rice through the aromatic oil for about 2 minutes. The grains should become glossy, with a lightly nutty aroma as their surface moisture evaporates.
Combine the tomatoes, chicken broth, crumbled bouillon, paprika, cumin, salt, and pepper with the rice. Stir until the seasonings spread evenly through the tomato-colored liquid.
Let the mixture reach a boil, then cover and lower the heat for an 18- to 20-minute simmer. At the end, the grains should feel tender and the pan should have absorbed the liquid.
Move the covered rice pan off the heat for a 5-minute rest. The trapped steam helps finish the upper grains without further browning the bottom.
During the rice cooking time, coat both sides of the sirloin strips with Montreal steak seasoning. A uniform coating distributes the peppery flavor across the beef.
Heat the reserved 1 tablespoon olive oil and butter in another skillet over medium-high heat, then sear the steak, allowing about 4 to 5 minutes per side for thicker strips and checking thin strips sooner. Watch for browned surfaces, but judge doneness separately because thickness changes the timing.
Loosen the rested rice with a fork, arrange the cooked steak across it, and drizzle generously with warm white queso. The topping should flow over the beef rather than fall in cold clumps.
Finish with fresh cilantro and, if desired, the optional warm flour tortillas. The cilantro adds a fresh contrast to the rich cheese and browned beef.