In a small bowl, thoroughly mash 1/2 ripe avocado.
Generously coat one side of the bread slice with butter. Place on a nonstick baking sheet and broil on LOW for 3-5 minutes, or until golden brown.
Remove from oven, flip, and spread avocado on the soft/untoasted side of the bread.
Top with cheese, bell pepper, and chili powder. Return to oven and broil on LOW for additional 2-4 minutes, or until cheese has melted.
Garnish with lime juice and enjoy while warm.