To make the caponata: Pour the oil in a large, deep skillet over medium heat. Add the anchovies and red pepper flakes and cook and stir for a few minutes to create a base flavor. Fry the eggplant in the anchovy oil, until it gets brown and sticky, stirring often. Add the tomatoes, red pepper, onion, and garlic, continue to cook until the vegetables break down and soften, about 15 minutes. Toss in the capers, raisins, olives, balsamic vinegar, sugar, and basil; season with salt and pepper. Lower the heat and slowly simmer until thick, about 20 to 30 minutes. The caponata tastes great hot, cold or at room temperature.
To make the lemon creme fraiche: Put the chicken stock, garlic, and lemon zest in a saucepan and place over medium heat. Simmer gently until the stock is reduced by half and thickened slightly. Take the pot off the heat, fish out the garlic, and add the creme fraiche. Just before you are ready to plate the dish, buzz the sauce with a handheld blender until it's thick and frothy.
To make the tuna: Rub a little olive oil on the piece of tuna. and season with a fair amount of salt and pepper. Put the chopped herbs in a flat dish and roll in the herbs to coat. Place a large skillet over medium-high heat and coat with 2 tablespoons of olive oil. When the oil gets hazy, lay the herb-coated tuna in the hot pan and sear for approximately 1 1/2 minutes on each side; as the tuna cooks, the red meat will become whiter. Transfer the tuna to a cutting board and slice.
To serve: Spoon the caponata on the bottom of 2 plates, lay the herb-seared tuna slices around the center, and drizzle the whole thing with the frothy lemon creme fraiche sauce.