Combine first 2 ingredients; microwave for 30-60 seconds to soften. Spread butter on 2 slices of bread. On the other side of one slice spread garlic basil mixture. Place that slice butter side down in skillet; layer with Muenster cheese, tomato, and basil on top. Place the other slice of bread on top with butter side up. Grill sandwich on both sides, 3-5 minutes until golden brown.
Suggested side: your favorite soup.