Combine buttermilk, sugar and butter in a large pot over medium heat, stirring frequently.
Once it comes to a light boil, turn the heat to medium low and cook for 3 more minutes, or until it turns a golden yellow color.
Remove immediately from the heat and stir in the baking soda and vanilla. Serve over pancakes while warm.
Store in a closed jar in the fridge for up to 2 weeks. Warm in the microwave in 30-second increments until the syrup is warm.
Tip: Use a pot bigger than you think because this syrup will bubble up while cooking. To turn this into a thicker caramel syrup, add 2 Tablespoons of Karo syrup in with the butter. Allow the syrup to cook for 5-8 minutes, stirring frequently. Once it turns a nice caramel color, remove from heat and stir in the baking soda and vanilla.