Heat the olive oil in a pan with a tight lid, then briefly saute the onion with the garlic.
Add the chicken broth and about ½ the pesto. When the liquid starts to boil, stir in the rice.
Lower heat to a simmer, cover and cook until rice is tender and all liquid is evaporated.
In a separate pan, melt the butter and saute the shrimp just until pink.
Stir in the lemon juice.
Combine the shrimp mixture and the parmesan cheese with the rice, folding gently.
Season with salt.
Garnish with the remaining pesto.