If you don't have pre-rolled puff pastry sheets, roll out the puff pastry into a rectangle shape on a piece of parchment paper. You want it to be about 10" x 14", but its really not a big deal whatever size it turns out to be. If you have pre-rolled sheets, just unroll and move on.
With a sharp knife, score the pastry about 1/2 an inch around the edges. This allows the edges to rise nicely around the tart.
Spread the sundried tomato pesto all over it and then sprinkle with a little of the cheese. Lay the asparagus down across the tart. Then sprinkle the peas and the tomato halves over top.
Next break up pieces of the prosciutto and place them all around the tart. Top the tart with the rest of the gruyere cheese.
Slide the tart on its parchment paper onto a cooking sheet and place in the oven. Cook for about 15 mins or until the edges are nicely browned.
Sprinkle the basil on the tart when you take it out of the oven, cut it in to pieces, and serve right away!