Heat olive oil in a large skillet. Add diced tomatoes, minced jalapeños, diced onion and a large pinch of salt and cook over moderately high heat, stirring often, until softened, about 5 minutes. Pour in tequila and cook, stirring frequently, until skillet looks nearly dry, about 2 minutes.
Reduce heat to low. Add cheese slowly, a little at a time, and cook, stirring constantly, until fully melted, about 30 seconds. Quickly transfer queso fundido to a serving bowl. Sprinkle cilantro on top and serve immediately, with tortillas or chips.