In a small saucepan, combine water and sugar over medium heat. Stir until sugar dissolves.
Add orange slices or zest. Simmer for 10–15 minutes.
Remove from heat. Cool slightly, strain, and store syrup in the fridge for up to 2 weeks.
Fill a glass with ice. Add espresso or coffee.
Stir in 1–2 tablespoons orange simple syrup. Pour in milk.
In a small jar or frother, combine heavy cream and 2 tablespoons orange simple syrup. Froth until light and airy.
Slowly pour frothed cream over the latte.
Top with fresh orange zest before serving. (optional)