Place water, dandelions and lemon in a pot and bring to a boil. Simmer, uncovered, for 20 minutes.
Turn off the heat and allow this to sit overnight.
Strain out the flowers and lemon using a colander, reserving the liquid left behind.
Measure the liquid left over, and place it in a pot with equal parts (weighted) white sugar. Bring to a boil, and simmer until desired consistency is achieved for approximately 25 minutes. If not thickening adjust sugar level as needed and continue to simmer.
The liquid will firm up further once off of the burner, so take it off before it thickens too much.