1. Preheat oven to 200 degrees. Heat a large skillet over medium- high heat. Slice polenta into 8 pieces. Add 1 tbsp. oil to hot pan, then add polenta. Cook until crispy, about 5 minutes per side. Transfer polenta to baking sheet and place in oven to keep warm.
2.add remaining 1 tsp oil to hot pan, then stir onion, bell pepper, and garlic. Cook until vegetables soften and brown slightly, about 5 minutes. Add tomatoes and oregano; cover and cook over medium heat for 5 minutes; stirring occasionally. Add salt, pepper, and shrimp. cook 5 another 5 minutes, stirring frequently, until shrimp is pink and opaque. Remove from heat and stir in lemon juice, plus salt and pepper to taste.
3. Divide polenta, among 4 plates. top with shrimp and serve immediately.