In Spain, we can buy it easier than sugar, however if you would like to make it, which you can keep in a jar in the fridge.....
ingredients are easy...
100g sugar
squeeze of lemon
water (opcional)
Without the water just place the sugar and squeeze of lemon in the tin you are going to use for the dessert over the heat until it turns darkish brown, then add the mix on top.
To make a lighter caramel, to use and pour over dessert and keep/store in the fridge for further desserts, use 200g sugar in heavy..ish frying pan, or pan with a squeeze of lemon, when it starts to turn light brown, remove from heat, stirring and slowly adding 200g water. Place back on heat until it turns brown in the centre. Stir with a wooden spoon so that it stays liquid and remove from heat. Use as needed, and store the rest in a jar or bottle in fridge.
Good luck