Pre-heat the oven to 200°C.
Brush the tuna steaks with half of the olive oil and mix with half of the thyme sprigs. Cover and chill until needed.
Heat the remaining olive oil in a large saucepan set over a medium heat. Sweat the onion and garlic for 6-7 minutes, stirring occasionally until softened. Add the tomatoes, peppers, smoked paprika and seasoning and continue to cook, covered, for 8-10 minutes until the tomato and peppers are soft.
Meanwhile, heat a frying pan over a high heat until hot and sear the tuna steaks until golden brown on both sides. Transfer to a lined baking tray and finish cooking in the oven for 4-8 minutes depending on desired doneness.
Add the sliced olives and remaining thyme sprigs to the sauce and adjust the seasoning as necessary.
Remove the tuna steaks when ready and allow to rest, covered with aluminium foil for a few minutes.
Spoon the sauce into serving bowls and top with the tuna steaks. Serve immediately.