Grilled Octopus Salad

Octopus

• 1 large (or 2 small) octopus, about 2 1/2 lb (1.1 kg)
• 8 cups (2 litres) water
• 2 onions, halved
• 2 celery stalks, cut into chunks
• 3 tbsp (45 ml) lemon juice
• 1/2 tsp salt
• Olive oil, for brushing

Salad

• 1/2 small red onion, thinly sliced, soaked in water for 10 minutes, then drained
• 1/4 cup (60 ml) olive oil
• 1/4 cup (10 g) flat-leaf parsley, chopped
• 1 tbsp (15 ml) capers
• 4 tsp (20 ml) lemon juice
• 1 pinch red pepper flakes