Homemade lemonade is like a just like that light scarf that works for multiple seasons or that trusty denim jacket that carries you from spring through fall. This rosy hued and infused lemonade spiked with sour tonic is all that and more. —Katherine Hysmith
For the rose simple syrup: Combine all the ingredients in a small sauce pan set over medium high heat. Bring to a bowl then lower to a simmer, heating until the sugar is completely dissolved and the whole kitchen smells of roses. Remove from heat and let cool. Strain the contents, discard, and transfer syrup to an airtight container until ready to use.
To assemble the lemonade: In a tall pitcher, stir together the lemon juice, tonic, and simple syrup. Fill the rest of the pitcher with cold water or seltzer. Add more syrup or tonic to taste. To serve, fill small glasses with ice, top with lemonade, and garnish with a lemon slice.