1. Boil the chopped potatoes in a large pot of salted water for 15-20 minutes, or until they're tender when pierced with a fork.

2. Drain the potatoes in a colander and let them cool to room temperature.

3. In a large bowl, combine the cooled potatoes, tomatoes cut in half, and a handful of chopped fresh dill.

4. In a small bowl, whisk together 2 tablespoons (30 ml) of white wine vinegar, 1/4 cup (60 ml) of olive oil, a pinch of salt, and a few grinds of pepper until well combined. Pour this dressing over the potato mixture and toss everything together until the potatoes are evenly coated.

5. In a separate bowl, mix together 1/2 cup (120 g) of tuna roe, 2 tablespoons (30 g) of mayonnaise, 1 tablespoon (15 g) of crème fraiche, and some chopped chives if you're using them. Season this mixture with salt and pepper to taste.

6. To serve, place a generous helping of the potato salad on a plate and top it with a dollop of the tuna roe mixture. If you like, garnish with some extra chopped chives.