Make your dressing. Combine the juice of 1 lemon and the rest of the ingredients in a small bowl and whisk together. Season to taste with salt and pepper.
Remove the rind from the melon and cut into bite sized pieces. Alternatively, use a melon baller to get round melon balls.
Place the arugula in a bowl.
Place the cantaloupe across the lettuce.
Tear each slice of prosciutto into approximately 4 pieces. Scatter the ham across the salad.