Preheat oven to 400 degrees and line a baking sheet with foil.
Remove the woody ends of the asparagus and toss the spears with olive oil, then sprinkle with the sea salt and pepper. Spread the asparagus spears out onto the prepared baking sheet and roast for 8-10 minutes or until slightly brown.
Meanwhile, slice the cheese and butter the bread. Remove asparagus from oven.
Heat up a large skillet over medium heat. Add two slices of the bread, butter side down, to the pan. Add cheese then add 3 spears of asparagus to each sandwich. Top with the other bread slices, butter side up.
Toast for 3-4 minutes then flip and toast for 2 minutes. Remove from heat and serve hot with tomato soup!
If you choose only one cheese for this sandwich go for the gruyere! It's a perfect pair with the asparagus and melts really well. Some grocery stores also sell a cheese that is a combo of white cheddar and gruyere, if you can find that go for it!