Sweet Potato, Apple and Onion Galette

Grad school homework procrastination means I am back to both cooking and blogging in a big way.  Please no judgement, writing about wrapping fall's best foods in pie crust and calling it dinner is infinitely more enjoyable than working on my first midterm paper.  I made this (a slight variation on this) on a lovely fall evening in Boston, served with a bowl of tomato soup (and a pumpkin beer) it was exactly the sort of indulgence that helps you appropriately enjoy a season.

Serves 4 as an appetizer, 2 as part of a main course

1 single refrigerated pie crust (If I had had premade pie crust on hand, I would have been tempted to speed the dinner process along by using it.  However, that's why I don't keep storebought pie crust on hand- it really is so much better when you make it yourself, even when you mess it up slightly and it's hard to roll out or too sticky) (Requested edit: I like smitten kitchen's and Joy the Baker's pie crusts, if you are in need of a trusty recipe)
1 small sweet potato, or half a large one (peeled, cut in half lengthwise and sliced)
1 apple, cored and sliced
1 quarter of an onion, thinly sliced
1/4 cup sharp white cheddar, cubed
1 tsp sage
1 tsp rosemary
2 T butter, cubed

Preheat oven to 375.

Roll out pie crust on a flat surface, transfer to a baking pan (do this before filling the crust, don't make the same mistake I did).  Dab crust with a few cubes of butter and cubes of cheddar, gently shake some of the spices over.  Artfully layer the sweet potato, apple and onion slices, starting with a circle in the middle and tucking butter and cheddar cubes throughout.  Be sure to leave 3/4 - 1 inch around the edge for the crust.  When finished, top with any leftover butter and cheddar, and the rest of the spices.  Use your discretion on the amounts of apple, sweet potato and onion - you want the same amount of apple and sweet potato, less onion, and for your crust not to be overloaded.  Fold the edge of the crust over the edges.  Because this is a galette, it's supposed to be a little imperfect compared to its fussy cousin, pie.  Bake for 40 minutes, rotating halfway through.

Serve with a bowl of soup or a hearty salad, or as the sort of appetizer that makes the main course feel embarrassed to follow.  I would imagine that if you caramelized the onions, this would be even better, but didn't get to that point last night - let me know if you do.