In a large bowl, whisk flour, and baking powder together until combined; set aside.

In a medium saucepan, combine pumpkin purée, sugar, cinnamon, salt, and nutmeg, and cook over medium heat, stirring constantly, until thickened and glossy and reduced to about 1 cup, 6 to 8 minutes. Remove pot from heat; whisk in oil, milk, and vanilla until combined. Let mixture cool for 5 minutes. Whisk in eggs until well combined and mixture is homogeneous.

Pour pumpkin mixture into flour mixture and stir gently until just combined (batter should remain lumpy with a few streaks of flour). Let batter sit for 10 to 15 minutes before cooking.

In a 12-inch nonstick skillet or a well-seasoned cast iron or carbon steel skillet, heat 1 teaspoon oil over medium-low heat until shimmering, 5 minutes. Using paper towels, carefully wipe out excess oil, leaving thin film on bottom and sides of skillet. To Test Temperature of Skillet: Drop 1 tablespoon batter in center of skillet. If pancake is pale golden brown after 1 minute, skillet is ready. If it is too light or too dark, adjust heat accordingly.

Using ¼-cup dry measuring cup or ice cream scoop, evenly space 3 portions batter in skillet. Use the back of a measuring cup or a spoon to gently spread each portion of batter into a 4-inch round. Sprinkle each pancake evenly with about 1 tablespoon pecans. Cook until bubbles on surface are just beginning to break, edges are set, and bottom sides are golden brown, 2 to 4 minutes.

Using a thin, wide spatula, flip pancakes and continue to cook until the second sides are golden brown, 1 to 3 minutes longer. Transfer to a plate and serve. (Alternatively transfer cooked pancakes to a wire rack set in a rimmed baking sheet, and hold warm in a 200℉; 93℃ oven until ready to serve.) Repeat with remaining batter and pecans, using additional oil as needed.