Beef and Caramelized Onion Toasts | RICARDO

Ingredients

• ½ cup (125 ml) sour cream
• 1 tbsp (15 ml) whole-grain mustard
• 1 tbsp dill, finely chopped
• 1 tsp (5 ml) prepared horseradish (optional)
• 1 lb (450 g) beef top sirloin steak, ¾ inch (2 cm) thick
• 2 tbsp (30 ml) olive oil
• 2 small red onions, thinly sliced
• ¼ cup (60 ml) water
• 4 slices country bread, each ¾ inch (2 cm) thick, toasted
• ¾ cup (20 g) arugula
• Sharp cheddar cheese shavings, to taste (see note)