Preheat the oven to 400°F / 205°C. Line a baking sheet with parchment paper. Split 2 bolillo rolls lengthwise and spread the cut faces with 2 tablespoons of softened salted butter.
Toast butter-side down in a skillet over medium-high heat for 3-5 minutes, until golden. Transfer to the baking sheet, cut-side up.
Divide 1 cup of refried beans and 1 cup of grated Monterey Jack over the bread. Bake for 12-15 minutes, watching closely, until the cheese melts and bubbles.
Top with ½ cup of pico de gallo and 1 diced avocado. Serve immediately.
