Heat the olive oil and butter in a nonstick pan over medium. Saute the onion, celery, peppers, and garlic for 3 - 5 minutes until the vegetables start to soften. Add the cajun seasoning and cumin, stir to combine.
Stir in the flour and cook for 1 minute.
Add the diced tomatoes and chicken broth. Stir until everything is evenly combined, bring to a simmer for about 15 minutes, stirring every couple of minutes. The sauce should thicken as it cooks. Taste to adjust the seasoning. Add in the shrimp and simmer for another 5 minutes. Season to taste with salt and pepper before serving.