Whichever dough you've made, wrap or cover the ball and leave to set in the fridge.
Preheat your oven to 200° C - 390° F.
Heat 2 T - 15 ml of olive oil in a skillet. Divide 1 T - 15 g of sugar across the bottom of the pan before placing the slices of fennel into the pan in a single layer (or as single as you can get it). Add a pinch of salt and pepper and leave to caramelize on a medium-low heat for at least 10 minutes, until the fennel has colored a nice golden brown.
Now turn the fennel over, again in as single of a layer as you can get, toss over 1/2 T - 7.5 g of fennel seeds and season with additional pepper and leave to brown for another 10 minutes. Turn off the heat, but leave the fennel in the skillet.
Depending on the weather you can now sprinkle the fennel with 1/2 c - 75 g of feta (if it's cold) or sprinkle over the feta right before serving (if it's warm).
Take your dough from the fridge and roll it out in an even layer in roughly the same diameter as your frying pan. To make it easier to place the dough onto the fennel in a second, it's best to do this on some parchment. The dough will break in areas but you can just stick it back together, it's fine.
Say a quick prayer and flip, toss or manoeuvre (I love a manoeuvre) the dough onto your fennel. Pat it down a little to make sure the dough adheres to the fennel and tuck in and cut off any excess edges before baking your tatin in the preheated oven for 25 minutes. The dough will stay pale but be cooked through, I promise.
Turn out the tatin by placing a large plate or board over your skillet and flipping the whole thing over (ask for assistance with this if you have someone around and are a bit of a klutz) and top with the 1/2 c - 75 g of feta if you haven't already used this. Sprinkle over the fennel fronds to make it pretty (or don't) and serve with a simple green lightly dressed salad.