How to Make It
In a medium saucepan, bring quinoa and 1/2 cup water to a boil. Reduce heat to medium-low, cover and simmer until water has absorbed, about 15 minutes. Remove from heat and let stand, covered, for 5 minutes. Transfer to a bowl and let cool. Stir in scallion greens and 1/4 tsp. salt.
In a small skillet, toast pumpkin seeds with a pinch each of chili powder and salt over medium heat, stirring occasionally, until seeds begin popping and become fragrant, about 3 minutes. Transfer to a small bowl and let cool.
Combine mango, 4 Tbsp. lime juice, 2 Tbsp. oil, cilantro and a generous pinch of salt. Toss black beans with cumin and remaining 1 tsp. oil. Stir together avocado and remaining 1 Tbsp. lime juice.
Divide salad ingredients evenly between 2 1-quart-capacity containers, arranging mango salsa, quinoa, black beans, red pepper, avocado, corn and pumpkin seeds in both. Cover containers. Salads will keep, covered and refrigerated, for 2 days. Let containers sit at room temperature for at least 20 minutes before serving. Shake container before eating to distribute ingredients.