Shrimp Risotto with Buttery Tomato Sauce

Make the shrimp broth
0 Put the shrimp shells, celery, garlic, salt and herb sprig in a medium (2-3 quarts) saucepan. Pour in the broth or water. Bring to a simmer over medium-high heat and cook 10 minutes — adjust the heat as needed so the broth doesn't come to a full boil. Strain the broth into a heatproof bowl or small saucepan, discarding the solids. Set aside and keep warm. 
Cook the shrimp
1 Heat the olive oil in a large (12-inch) non-stick skillet over medium-high heat. Add the shrimp in one layer and season with a pinch of salt and black pepper to taste. Cook 2-3 minutes, then flip the shrimp over. 
4 Stir in the tomato paste, garlic, oregano, and red pepper so they're distributed evenly with the shrimp. Cook 1-2 more minutes, until the shrimp are cooked through. Remove the pan from the heat and add the shrimp broth and butter, swirling the pan until the butter melts. Partially cover the pan to keep warm and set aside.
Make the risotto
6 Heat the olive oil in a deep saute pan or Dutch oven over medium heat. Stir in the shallot or onion and cook until it's softened and translucent (don't let it brown), 2-3 minutes.
8 Add the rice and cook one minute, stirring well to evenly coat the grains in the oil. 
7 Pour in the wine and let it bubble until most of it is evaporated. Add 1 cup of the shrimp broth and turn the heat up to medium-high. Cook until the liquid is nearly gone, stirring occasionally to keep the rice from sticking.
9 Continue adding broth, ½ cup at a time, maintaining a lively simmer and stirring occasionally. After about 15 minutes, when you've made 4 additions (a total of 3 cups) of the broth, the rice grains should be almost done.  The kernels will look swelled and the center of the rice should have an al dente bite. 
11 Continue cooking about 5 more minutes  if needed —  you probably won't use up all the broth. It's fine if there's some liquid in the pan when the rice is ready, as it will continue to absorb as it sits. If the risotto looks dry, stir in a little more broth, ¼ cup at at time to reach a loose, creamy consistency.
10 Remove the pan from the heat and stir in the grated cheese and parsley or basil. Spoon the risotto into serving bowls. Top with some of the shrimp, including the sauce from the saute pan. Squeeze some lemon juice over each portion of risotto and serve.