To Make the Lemonade: Over a gas burner or under a broiler set on high, roast the chile, turning occasionally, until skin is blackened on all sides.
Remove the skin, open, and remove seeds and stems.
Put roasted chile, bell pepper, agave syrup, lemon juice, and water into a blender and process until thoroughly combined.
To Make the Hatch Margarita: In a medium bowl, combine garlic powder, cumin, sugar, salt, and bell pepper powder and stir to combine. Wet rim of rocks glass (or cowboy-boot glass!) and dip in mixture to rim glass. Put ice, vodka, mezcal, and lemonade in the glass; stir and serve.