Steak Griddle Fajitas

Ingredients

• 1 large white onions
• 1 tsp ground cumin
• 1 large yellow bell pepper
• 1 large green bell pepper
• 1 tsp black pepper
• 1 ¼ cup beer
• 1 large red bell pepper
• 2 garlic cloves
• 2.2 lb Flank Steak