DRESSING: Place the sugar, water, orange juice and orange zest in a small pan over medium heat. Stir until the sugar is dissolved and bring to a boil. Lower the heat and simmer for about 15-20 minutes or until slightly thickened. Transfer mixture to a Mason jar and stir in the vanilla extract. Add a tiny pinch of salt if desired (to intensify flavor). Put the lid on the jar and refrigerate until ready to serve. This helps concentrate and intensify flavors. You don't want to pour the dressing over the fruit if it is at all warm.
FRUIT SALAD: Prepare the fruit by washing and thoroughly drying (wet fruit waters down the salad). Remove the stems and thinly slice the strawberries. Remove any stray stems from the blueberries. Remove the pits and thinly slice the peaches. Remove any leaves/stems from blackberries. Combine all the fruit in a large bowl and gently toss. Tear off and add in a few mint leaves if desired. Pour the cooled dressing over the fruit and gently toss again.
STORAGE: Fruit Salad is best enjoyed the same day it is dressed. If you'd like to have leftovers, store dressing and salad separately and only add dressing to the salad.