Heat the olive oil in a large skillet over medium-high heat. Add the sausage and cook, stirring, until browned, about 2 minutes. Remove to a plate with a slotted spoon.
Add the potatoes to the skillet and cook until lightly browned, 3 to 4 minutes. Add the onions and fennel and stir to combine; season with 1/2 teaspoon salt and a few grinds of pepper. Cook, stirring occasionally, until the onions and fennel just begin to soften, 4 to 5 minutes.
Make a space in the center of the skillet and add the tomato paste. Cook, stirring, until the tomato paste darkens slightly, about 1 minute. Add 1 cup water and stir everything together. Reduce the heat to medium low, cover and cook until the vegetables are tender, 7 to 8 minutes.
Return the sausage to the skillet along with the vinegar and honey. Simmer, uncovered, until the liquid reduces to a glaze, about 2 minutes. Season with salt and pepper. Divide among bowls and top with fennel fronds.