Preheat your oven to 350 degrees F. Generously grease and flour a 9" or 10" springform pan and set aside.
Place the pecans in a single layer on a rimmed baking sheet. Bake in your preheated oven for 12-15 minutes. Remove the pan from the oven and cool.
In a food processor, pulse together the flour, 3 cups of the toasted pecans, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with the paddle attachment, cream together 3/4 cup (1 and 1/2 sticks) of the butter, sugar, and orange zest on medium speed for about 4-5 minutes until light and fluffy. Add the egg and egg yolk and continue to mix for another minute. Add in 3 Tablespoons of the rum. Stop the mixer and add in the dry ingredients. Mix on low until everything just comes together.
Transfer the batter to your prepared springform pan, making sure to smooth the top. Bake in your preheated oven for 45-50 minutes or until a toothpick inserted in the center comes out clean. The torte should be golden brown. Allow the torte to cool.
Meanwhile, make the butterscotch topping. In a small saucepan over medium heat, mix the brown sugar, 1/2 cup of the cream, the remaining 1/4 cup (1/2 stick) of butter, and remaining 1 Tablespoon of rum to a boil. Stir often and continue heating until the mixture thickens, about 3 minutes. Remove the pan from the heat and stir in the remaining 3/4 teaspoon salt. Then fold in the remaining 2 cups of toasted pecans and stir until the mixture has cooled down but is still spreadable.
Top the torte with the butterscotch pecan mixture. Make whipped cream with the remaining cream by whipping the 1 cup of heavy cream in a large bowl (using either a handheld mixer or a stand mixer fitted with the whisk attachment). Top with whipped cream if desired.
The torte can be baked 1 day ahead. Store tightly wrapped at room temperature. The butterscotch (without the pecans) can be made up to 3 days ahead. Gently reheat it over low heat until pourable, then add pecans.
Leftovers should be covered and stored at room temperature or in the refrigerator and will keep for several days.