Add sugar to a saucepan and heat the sugar on medium low heat until completely melted and amber in color. Make sure to swirl the pan gently or stir with a rubber spatula every 30 seconds to prevent it from burning. The sugar will form clumps before melting slowly. Be patient and keep an eye on it to make sure it does not burn. While the sugar is heating on the stove, prepare your hot water- use an electric kettle, stove or microwave to heat the water, then set aside.
Once the sugar has fully melted and is amber colored (a golden orange/brown color), carefully and slowly pour in the hot water and then stir with a whisk or rubber spatula to combine. Note the mixture will bubble, that's normal. If some of the sugar hardens and crystallizes, that's okay. It should melt and liquify once you bring the mixture to a boil.
Add in the salt, and then bring the mixture to a roaring boil with lots of scary bubbles.
Once the syrup is boiling, reduce the heat to a medium simmer and let simmer for 10 minutes. You don't need to stir or touch the syrup.
After 10 minutes, turn off the heat and remove the syrup from the burner. Let the syrup cool for 2 minutes, then add in the butter extract and stir to combine.
Taste the syrup and add more salt or butter extract if needed.
You can use the syrup immediately in any drink of choice or let the syrup cool at room temperature before adding to an airtight syrup bottle or mason jar, and store in the fridge for up to 3 weeks.