Make a pie crust. Prick the crust with a fork, and/or cover it with a circle of parchment paper and sprinkle it with pie weights, then blind-bake the crust until it just starts to brown (10-15 minutes).
Prepare 1 pound of pumpkin puree. You can purchase this in a can, or make it fresh by roasting a quartered pumpkin or other hard-skinned winter squash for 30-45 minutes until soft, then allowing it to cool and separating the flesh from the skin and pureeing in a food processor.
Bring the pumpkin to a simmer for a few minutes to reduce moisture.
Season the pumpkin to taste: perhaps 1/2 tsp salt, and 2 tsps total of a blend of “warm” spices like cinnamon, nutmeg, ginger, allspice, cloves, pepper, etc — what medieval cooks might have called “fine powder” or what Americans now call “pumpkin pie spice.”
Set the pumpkin aside to cool for a few minutes.
Combine 3 eggs, 1 cup of half-and-half (or equal parts milk and cream, or just cream), and 3/4 cup of sugar, and whisk them together.
Stir together the pumpkin and the custard, then pour them into the pie shell.
Bake at 350° for about 45 minutes, rotating half way through. At around 35 minutes, start checking every five minutes to see if top is lightly browned and the custard has set — it’s okay for the center to still jiggle, but it shouldn’t be wet.
Allow to cool before serving.
See also: Marlborough pie, which is similar but uses apples instead of pumpkin.