1. Saute the onions in the heated oil in a large skillet over medium heat until tender.
2. Cool the onions to room temperature.
3. Cut a slice from the top and bottom of each melon.
4. Place each on end and remove the peel, cutting from top to bottom.
5. Cut into halves, discarding seeds.
6. Cut 1 honeydew half and 1 cantaloupe half into 1 inch wedges.
7. Arrange those wedges on a serving platter.
8. Cut the remaining melon into 3/4 inch chunks and combine with the mint, lime juice and pepper in a bowl and toss to mix well.
9. Spoon this over the arranged melon wedges and top with the onions, feta cheese and pine nuts.
10. Chill until serving time and toss to serve.