Prepare broccoli, cauliflower, red onion and sundried tomatoes as noted above and place in a large bowl.
Toast the pine nuts: place the nuts in a dry skillet (no oil) over medium heat. Heat, shaking the pan and stirring often with a wooden spoon, until the nuts are fragrant and golden brown, about 3 minutes. Remove immediately from the heat and transfer to a plate to stop the cooking.
In a medium bowl, mix the mayonnaise, lemon juice, sugar, and Dijon mustard.
To the bowl of the vegetables, sprinkle in the kosher salt, then add the dressing, toasted pine nuts and feta cheese and stir. Taste and add a pinch or two more salt if necessary. Serve immediately or refrigerate until serving. Store refrigerated for up to 3 days (if making in advance, add pine nuts directly before serving).