Melt butter in a large nonstick skillet over medium heat. Add onions; cook 2 minutes. Add rice, quinoa, and millet; cook 3 minutes, stirring frequently. Stir in broth and salt. Bring to a boil; cover, reduce heat, and simmer 20 minutes or until liquid is absorbed.
for your toddler: Serve a spoonful as a side dish with meat, fish, poultry, or tofu.