Preheat the oven to 350°F (180°C). Rub butter along the sides and bottom of the loaf pan. Add flour to the pan and rotate it around to coat the sides and bottom. Line the pan with parchment paper and use clips to hold the paper in place. When the bread is done, the parchment paper is used as a sling to lift the bread out of the pan.
Melt the butter in a small saucepan over low heat. Melting over low heat prevents splatter and reduces the amount of evaporation. Remove the butter from the heat and set it aside.
Put the flour, salt, baking soda, and baking powder in a medium-sized bowl. Whisk for 30 seconds to combine.
Place the granulated sugar, brown sugar, and pumpkin pie spice in a large bowl. Use a whisk to combine. Use your fingers to break up any brown sugar clumps.
Add the eggs and vanilla extract and whisk for 1 minute. The mixture will be thick and lighter in color. Add the melted butter, whisk until incorporated, and then add pumpkin puree and whisk to combine. Let the mixture sit for 10 minutes.
Toss the cranberries with the flour mixture until the cranberries are coated with flour. Add half of the flour mixture to the wet ingredients and mix with a silicone spatula until the flour mixture and cranberries are mixed in. Add the remaining flour mixture and fold it into the batter until no white bits of flour are visible. There may be a few lumps and that is okay. Do not overmix.