Preheat the oven to 220°C/425°F. Mix together the smoked paprika, oregano, chilli powder and cumin in a small bowl. Rub the fish fillets with half the oil and then dust liberally in the spice mixture. If time allows, set aside for 10 minutes to allow the flavours to penetrate the flesh.
Put the baby new potatoes in a steamer and add a pinch of salt. Cover and cook for 15-20 minutes or until cooked through and tender.
Arrange the lemon slices and bay leaves on a baking sheet and sit the spiced fish fillets on top, then arrange the vines of cherry tomatoes around the edges and drizzle with the remaining oil. Roast in the oven for 8–10 minutes, until the fish fillets are just cooked and a little charred and the roasted cherry tomatoes are beginning to split.
Using a fish slice, transfer some of the lemon slices and bay leaves with a fish fillet sitting on top onto warmed plates and place a vine of roasted cherry tomatoes alongside each one to serve. Place a bowl of the baby new potatoes on the table so that everyone can help themselves.