Add ½ cup sugar and ¼ cup water to a medium heavy-bottomed saucepan over medium/low and stir until the sugar has dissolved.
Bring the mixture to a simmer, continue to stir, and cook, scraping the sides of the saucepan, until golden, about 8-10 minutes.
Once the caramel has formed, add the remaining sugar and give it a stir.
Slowly pour in boiling water and lemon juice, stirring constantly. Whisk to combine until sugar completely dissolves.
Continue to simmer on medium/low heat, for about 15-20 minutes, until a rich amber color and a slightly thickened consistency.
Remove from the heat and set aside to cool completely.
Pour into a jar and keep it at room temperature for 10-12 weeks.
If the syrup is too stiff, add it to a saucepan and thin it out with some water until you get the desired consistency.
If the syrup is too thin once cooled, add it to a saucepan back on the stove for another few minutes to thicken up more.