Preheat the oven to 350 degrees.
Grease a medium casserole dish with 1 tablespoon of the olive oil. Clean the sardines by removing the heads and filleting. Season the fillets with salt and pepper. Season the flour with salt and pepper. Dredge the fillets in the flour, coating completely. In a large saute pan, over medium heat, add 1/4 cup of the olive oil. When the oil is hot, pan-fry the fillets, for a couple of minutes on each side until golden brown. Remove and drain on paper towels. Set aside.
Bring a pot of salted water to a boil. Add the pasta and cook al dente. In a saute pan, over medium heat, add the remaining 2 tablespoons of oil. When the oil is hot, add the saffron and onions. Season with salt and pepper. Saute until wilted, about 4 to 6 minutes.
Using the back of a fork, mash the anchovies to form a paste. Add the anchovies, garlic, fennel, sultanas, and pine nuts. Season with pepper. Saute for 2 minutes. Stir in the water and continue to cook for 1 minute. Remove from the heat. Drain the pasta and cool in cold water for a few minutes.
Toss the pasta with 3/4 of the anchovy mixture. Mix well. Season with salt and pepper. Spoon half of the pasta mixture into the prepared casserole dish. Lay the sardines over the pasta. Spoon the remaining pasta over the sardines. Pour the remaining anchovy sauce over the pasta. Place in the oven and cook for 10 minutes. Remove from the oven and serve.