Heat the olive oil in a large frying pan over a medium-high heat until shimmering.
Add the sausage slices and cook for 5–7 minutes, turning occasionally, until golden and crisp around the edges. Transfer to a plate and set aside, leaving the fat in the pan.
Add the chopped onion and peppers and cook over a medium heat for 8–10 minutes, stirring occasionally, until the onion is translucent and the peppers are just tender.
Stir in the crushed garlic and cook for 1 minute until fragrant.
Pour in the chopped tomatoes and chicken stock, then stir in the Cajun spice blend, salt and black pepper. Bring to a gentle simmer, scraping up any bits stuck to the base of the pan.
Return the sausage to the pan, stir well, and simmer for another 5–7 minutes until the flavours meld and the sauce has thickened slightly.