Preheat the oven to 350°F (175°C). Thoroughly grease an 8 × 4-inch loaf pan to help prevent sticking.
Place the pumpkin purée, brown-style sweetener, whole eggs, egg whites, cooled melted butter, and vanilla extract in a large mixing bowl. Whisk until the mixture is smooth and evenly blended.
Incorporate the coconut flour, egg white protein powder, baking powder, pumpkin pie spice, and salt into the pumpkin mixture. Whisk thoroughly until the batter is uniform and no dry lumps remain.
Add water gradually, approximately 1 tablespoon at a time, whisking after each addition. Use only enough water to create a thick batter that can be scooped and spread but cannot be poured. The mixture should retain its shape.
Transfer the batter to the prepared pan. Spread it evenly and level the surface with a spatula.
Distribute the chopped pecans evenly over the top of the batter, if using.
Place the pan in the preheated oven and bake for 55–65 minutes, or until the surface is golden brown and the loaf feels firm when lightly touched.
Remove the bread from the oven and leave it in the pan until fully cooled. Complete cooling allows the loaf to set properly and maintain its shape when sliced.