Pork Tenderloin Smothered in Onion and Mustard without apples

3 tablespoons olive oil 2 teaspoons fennel seeds , crushed 2 medium fennel bulbs , quartered, cored, thinly sliced 1 large onion , thinly sliced 2 tablespoons[...]

2 (12 ounce) pork tenderloin, cut into 2-inch lengths and pounded 1-inch thick salt fresh ground black pepper 1 teaspoon all-purpose flour , plus more for[...]