This sweet and salty combination is surprisingly refreshing.
Whisk together jam, juice and two vinegars in a bowl.
Add oil and whisk to combine.
Add salt and pepper to taste.
Melt butter in a non-stick skillet over medium heat.
Add sugar and pepper; stir to blend.
Add nuts and stir until nuts are coated. Transfer to a plate and cool. (These can be done in advance and stored in an airtight container until needed.)
Arrange watermelon slices around the edge of a large platter.
Toss greens with vinaigrette to coat and place in the center.
Top with nuts and onion slices.