Ribeye sandwich with caramelized onion – BBQ-Heroes

Ingredients

• 2 large white onions
• 100 gr butter (3.5oz)
• 2 tbsp honey
• water
• 1 tbsp balsamic vinegar
• 1 tbsp olive oil
• 300 gr rib eye (thick like 2.5 cm or 1 inch)
• 1 large loaf of bread for 6 thick slices
• 2 tbsp mustard
• 1 handful arugula
• 2 tbsp mayonnaise