Lightly grease a standard-size loaf pan with oil, then line it with a strip of parchment paper. Preheat the oven to 350 ℉.
In a large bowl, whisk the 3 large eggs, then whisk in the ¾ cup pumpkin puree, and ¼ cup oil until smooth, then whisk and stir in the 1 cup brown sugar, 1 ¾ cups oat flour, 1 teaspoon ground cinnamon, ½ teaspoon ground ginger, ½ teaspoon ground nutmeg, 2 teaspoons baking powder, and ½ teaspoon fine sea salt.
Pour the batter into the prepared pan, let it rest for 15-20 minutes, then bake for about 55 minutes, until a tester inserted in the center comes out clean. Cool the cake in the pan set on a wire rack for 15 minutes, then turn it out to cool completely.
Make the glaze: Whisk the melted 2 tablespoons unsalted butter, 2 tablespoons maple syrup, and sifted 1 cup powdered sugar together until smooth, then pour it over the loaf. Let the glaze set for about 15 minutes before slicing.
Notes
Sift the powdered sugar. Always sift powdered sugar before adding it to glazes or frostings to remove any lumps. It's especially important here because the glaze needs just 3 ingredients.
Don't forget the pumpkin seeds. A scant ¼ cup of pumpkin seeds adds a bit of contrast and visual interest to the smooth glaze and cake. You can add the seeds raw, as I did, or lightly toast them first. I prefer raw pumpkin seeds rather than salted.
Make it vegan. Substitute three flax eggs for the eggs. Happily, this cake is already dairy-free.
Use pumpkin pie spice. Use pumpkin pie spice in place of the combination of spices in the batter if you prefer.
Add chocolate. For a flavor boost, stir in 1 cup of semisweet chocolate chips into the batter.
Skip the glaze. I mean, why would you?! But if you want a slightly different presentation, sift powdered sugar over the top of the loaf, or drizzle slices with salted caramel sauce.