Place the drained red peppers, shallots, garlic, lemon zest, salt and pepper in the bowl of a food processor. Process until smooth.
Pour the mixture into a saucepan and heat until it starts to bubble.
Add the red pepper flakes and stir.
Gradually add the heavy cream, whisking as it goes in.
Melt some butter in a skillet.
Add the onions and saute until translucent.
Add the sliced yellow squash to the skillet and saute until fork tender.
Add some salt and pepper to taste.
Pour the sauce over the squash and gently stir until the squash is coated.
Before serving, top the with fresh sliced basil and a squeeze of lemon juice for added freshness and color.