In a large skillet over medium-high heat, melt butter until foaming. Add carrots, water, and salt (I like 1/4 teaspoon).
Bring to a simmer. Reduce heat, cover, and simmer until carrots are tender, about 5 minutes.
Stir in peas and continue cooking until heated through, about 5 minutes longer. Season to taste with salt and pepper.
Notes
Frozen peas: To quickly thaw frozen peas, rinse them under cool water in a strainer or colander until softened. Or, toss the peas in still-frozen (add an extra minute or 2 to the cooking time).
Yield: This recipe makes about 2 cups of buttery Peas and Carrots, enough for 4 servings, 1/2 cup each.
Storage: Store leftovers covered in the refrigerator for up to 4 days.
Make ahead: Peel and slice the carrots up to 3 days in advance (store covered in the refrigerator).