I couldn't convince my almost 4-year-old to try this (his response: "I refuse that it's delicious!")...but hey, more for us grownups! It really IS delicious. Caramelizing brings out fennel's sweetness (and of course does the same for the onions) and mellows it a bit without losing all its flavor. Properly caramelizing fennel and onions takes a bit of time (25-30 minutes or longer if you like) but it's worth it.
2 Tbsp olive oil
1 large or 2 medium fennel bulbs, thinly sliced
1 large onion, thinly sliced
1 Tbsp red wine vinegar
Salt and pepper to taste
1 14-inch pizza crust
3 oz. shredded mozzarella
1 Tbsp minced fresh sage
3 oz. goat cheese
Heat the olive oil in a large skillet or Dutch oven. Add the fennel and onion and stir to coat thoroughly with oil. Turn the heat to medium and cover. Uncover and stir well every 4-5 minutes or so, and adjust the heat downward if the vegetables are getting too browned (as opposed to caramelized). They will slowly cook down, getting soft and golden over the course of at least 25-30 minutes. If you have time you can continue to caramelize until they are much darker. Toward the end you will need to check on them more frequently and perhaps turn the heat even lower. When they are ready, stir in the red wine vinegar and add salt and pepper to taste. Remove from heat.
As the onions and fennel approach doneness, preheat the oven to 450 degrees and lightly paint the pizza crust with olive oil.
Sprinkle the shredded mozzarella over the pizza crust, then add the caramelized veggies. Sprinkle with sage, then dot with goat cheese.
Bake the pizza for 15-18 minutes, until the crust is done and cheese begins to brown.