In a large skillet over medium-high heat, heat the olive oil and butter until the butter melts. Add the celery, onion, and bell pepper. Saute until the veggies are soft, about 4 to 5 minutes. Add the garlic and cook for 30 more seconds.
Add the shrimp, Cajun seasoning, paprika, and sugar. Cook until the shrimp are just barely pink and opaque, about 2 to 3 minutes per side.
Stir in the diced tomatoes with their juices, broth, and lemon juice, scraping any browned bits from the bottom of the pan with a wooden spoon. Simmer for about 1 to 2 more minutes. Reduce the heat to low, stir in the rice, and cook just until the rice is heated through, about 1 to 2 more minutes. Add a splash of extra chicken broth to thin the mixture, if desired. Taste and season with additional salt and pepper if necessary. If you like a bolder, spicier flavor, add some extra Cajun seasoning.
Garnish with sliced green onions, chopped fresh parsley, hot sauce, and lemon wedges if desired.