Melt butter in a skillet over medium heat. Sauté garlic for 1 minute, then stir in milk and bring to a simmer.
Gradually whisk in cheeses until smooth. Season with chili powder, cumin, salt, and pepper. Keep warm.
Rinse rice. In a saucepan, heat olive oil and toast rice with garlic powder for 2 minutes. Add broth and salt. Boil, then simmer covered for 18–20 minutes until tender.
Rub steak with oil and spices. Let rest at room temp. Heat skillet until hot and sear steak 4–5 minutes per side. Rest 5–10 minutes, then slice thinly.
Spoon rice into bowls, top with steak and queso. Add cilantro, lime, avocado, and jalapeños. Serve hot.