Preheat your oven to 350°F (175°C). Grease a 9×13-inch baking dish or line it with parchment paper for easier cleanup. This gives the cake a head start and ensures nothing sticks.
In a large bowl, whisk together the pumpkin puree, eggs, granulated sugar, brown sugar, oil, and vanilla extract. The mixture should look smooth and creamy with a lovely orange hue.
In a separate bowl, whisk together the flour, baking soda, baking powder, salt, cinnamon, and nutmeg. Gradually add the dry ingredients to the wet, stirring just until combined. Be careful not to overmix so the cake stays tender.
Pour the batter into the prepared baking dish. Use a spatula to smooth the top evenly. The batter will be thick but spreadable.
In a small bowl, mix the toffee bits, chopped pecans (if using), brown sugar, melted butter, and a pinch of salt. Stir until everything is coated and crumbly.
Sprinkle the toffee crunch mixture evenly over the batter. Bake for 30 to 35 minutes, or until a toothpick inserted into the center comes out mostly clean with a few moist crumbs. Let the cake cool on a wire rack for at least 15 minutes before slicing.