Heat milk to 120 F. Do not boil. Combine warm milk with spinach in a blender and blend well.
In a large bowl, combine semolina, rye flour, bread flour, whole wheat flour, yeast, sugar, salt and paprika. Mix well.
Add spinach-milk and mix well. After the dough looks shaggy, start to knead by hand or if using the dough hook of an electric mixer, let the machine knead for 5 minutes. Knead for 10 minutes if kneading by hand, until the dough is smooth and elastic.
Place in a greased bowl. Cover with plastic wrap and a kitchen towel. Leave to rise until doubled in size, about 1 hour.
Pull the dough from underneath and pull over the top a few times. The dough will deflate.
Spray a Dutch oven with non stick spray. Place the dough in the pot, cover and leave until doubled in size, 45 minutes to an hour. Preheat oven to 450 F.
With a sharp knife, gently make two slits in the dough. The dough will slightly deflate. Brush the top with the buttermilk and then sprinkle sunflower seeds on top.
Place the Dutch oven, covered, in the oven and bake for 30 minutes. Uncover and bake another 10 minutes. The bread should sound hollow when tapped.
Remove from pot and leave until cooled completely.