Preheat your oven to 350°F (175°C). Grease and flour a 9x13-inch baking pan.
In a medium-sized bowl, combine the flour, baking soda, baking powder, and salt, using a whisk to blend them together. Set aside.
In a large mixing bowl, beat together the softened butter and granulated sugar until the mixture turns light and fluffy.
Add the eggs one at a time, making sure each one is fully mixed in before adding the next.
Stir in the vanilla extract.
Gradually add the dry ingredients to the wet ingredients, alternating with the buttermilk, beginning and ending with the dry mixture. Mix until just combined.
Evenly distribute half of the batter into the greased and floured pan.
In a small bowl, combine the cinnamon and chopped pecans (if using). Sprinkle half of this mixture over the batter in the pan.
Add the remaining batter on top and finish with the rest of the cinnamon-pecan mixture.
Use a knife to swirl the cinnamon-pecan mixture into the batter, creating a marbled effect.
Place it in the oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean.
Allow the cake to cool on a wire rack before serving.