Heat up the oil in a nonstick pan on medium-high heat. Add chopped shallots and sauté for 5 minutes. Add slices of fennel and sauté 10 minutes on each sides. Remove from pan. Add cherry tomatoes whole and sear on high heat for 5 minutes. Add the fennel and shallots back to the pan. Drizzle with olive oil and season with fleur de sel, pepper, onion and fennel pollen. Sauté gently for 2 minutes. Taste and adjust seasonings if needed.