Sea Bass Tartare
Preheat the oven to 250°C (approximately 485°F). Rinse the sea bass, pat dry, and finely dice. Add the lemon juice and grapeseed oil, then season to taste with salt and white pepper. Cover and refrigerate so the fish can marinate. Rinse, trim, and finely dice the celery. Blanch in boiling salted water for 2 minutes, then drain and mix with the sea bass tartare. Rinse and dry the peppers. Halve, remove the seeds, and roast in the oven until the skin is black and blistered.
Mix the balsamic vinegar and oil. Season to taste with salt, pepper, and sugar. Remove the peppers from the oven, cover with a kitchen towel, and let rest. Peel the peppers, julienne, and brush with the balsamic marinade. Cover the peppers, and let infuse briefly. Rinse and dry the arugula. Divide the peppers and arugula on plates, top with the sea bass tartare, sprinkle with the lemon zest, and serve with the flatbread.