Step 1

Heat 1 tablespoon butter in a large skillet over medium-high heat until melted and foamy. Add bell pepper, zucchini and jalapeño; cook, stirring often, until softened, 2 to 3 minutes. Add broccoli and stir to coat. Add ¼ cup water, cover the pan and cook until the broccoli is crisp-tender, about 3 minutes. Transfer to a medium bowl, draining off water if necessary. Wipe the pan clean.

Step 2

Spread the remaining 2 tablespoons butter over 1 side of each bread slice. Place the bread slices, buttered-side down, in the pan. Divide the vegetables among the bread slices. Top each with a slice of cheese and a bread slice, buttered-side up. Cook over medium heat until the sandwiches are lightly browned and the cheese is melted, 2 to 4 minutes per side. (Cook the sandwiches in batches if they don't all fit in your skillet.)

Step 3

Meanwhile, combine soup and the remaining 1 ⅔ cups water in a medium saucepan; cook  over medium heat, stirring occasionally, until heated through, about 3 minutes. Cut the sandwiches in half and serve with the soup.