Alfabetos Sopa De Tomate

Ingredients

• 4 tablespoons unsalted butter
• 1/2 large onion, cut into slices
• 1 (28-ounce) can whole peeled tomatoes
• 1 1/2 cups water, vegetable stock, or chicken stock
• 1/2 teaspoon fine sea salt, or more to taste
• 1 box Banza alphabets