Roll out the dough. It should be slightly more than ⅛ inch thick.
Sprinkle a sheet pan with cold water to keep the bottom of the tart from burning, and unroll the dough over the sheet pan.
Trim off the rough edges of the dough.
Dock the pastry with a fork to keep it from puffing.
Arrange the apples in rows, overlapping slightly and changing direction with each row.
Sprinkle the apples with the sugar and cover with thin slices of butter.
Bake the tart. After about 20 minutes, check to make sure the pastry isn’t puffing. If it is, poke the pastry with a paring knife to deflate it. If necessary, use the tip of the knife to reposition any apples.
Bake for another 20 to 30 minutes, until deep golden brown. Scrape under the tart with a metal spatula to loosen it.
Trim off the edges. It’s normal that these are slightly burned.