Heat the oil over medium heat in a large electric skillet. Add the onion, carrot, celery and garlic. Cook, stirring occasionally, until the vegetables are soft but not brown, about 8 minutes. Add the turkey, tomato paste, salt and red pepper flakes; cook, stirring, until the mixture turns dark red, about 10 minutes. Add the tomatoes and their juices, breaking the tomatoes into bite-size pieces with the side of a spoon.
Add the bay leaf and fennel seeds. Bring to a boil, reduce the heat and simmer, uncovered, stirring occasionally, until the sauce thickens, about 1 hour. Discard the bay leaf, season with salt and serve over pasta.