Heat 2 tablespoons olive oil and 1 tablespoon butter in a large pan or wok over medium heat.
Add the chopped red onion and cook for 2-3 minutes until softened.
Add the rice, turmeric, cumin, ½ teaspoon chili powder, pressed garlic, chili pepper, diced bell peppers, baby corn, black olives, and diced tomato. Stir and cook over medium heat for 3-4 minutes.
Pour in the vegetable stock and bring to a boil. Reduce heat to medium-low and simmer for 20 minutes, stirring occasionally and adding more stock gradually as needed. The paella should be moist but not watery or dry.
Add the cashew nuts and frozen peas, and simmer for another 5 minutes, stirring occasionally.
Season to taste with salt, pepper, and cayenne pepper, then serve.
Optional: For extra aroma, soak a few threads of saffron in hot water and use it instead of turmeric.