Preheat oven to 475 degrees. Line a large heavy-duty rimmed baking sheet with parchment paper and set it aside.

Using a sharp knife, cut the acorn squash in half lengthwise (through both the stem end and the pointy end).

Use a spoon to scrape out the seeds and fibers. Put each half, cut side down, on a cutting board and slice off about ¾ inch from each end and discard.

Slice squash crosswise into ½-inch-thick half-rings. If you want to, trim away any remaining fibers from the rings by running a paring knife around the inside of each half-ring.

Place the half-rings on the parchment paper.

In a small saucepan, melt the 2 Tbsp butter over low heat. Remove pan from the heat and add the maple syrup, vanilla, and cardamom, stirring to combine.

Use a pastry brush to lightly brush squash pieces with a little less than half the butter mixture.

Season the pieces very lightly with salt and turn them over.

Brush this side with the remaining butter mixture, reserving about 1 Tbsp for brushing on after cooking. If using a larger squash and you wind up with less than 1 Tbsp of liquid, add 1 or 2 tsp more butter to the saucepan. Season the tops very lightly with salt.

Roast the squash for 12 minutes in the oven. Use tongs to flip the squash pieces and continue to roast until they are nicely browned and tender, 10 to 12 minutes more. The bottoms of the pieces will be browner than the tops.

Remove the squash from the oven and flip the pieces over so that the browner side is facing up.

Reheat the butter mixture briefly over low heat if needed (or to melt the additional butter). Brush the butter mixture over the squash slices and serve.