Heat milk to 110°F. Place in a bowl of an electric mixer fitted with paddle attachment. Add yeast and 1 teaspoon sugar and let stand 5 to 6 minutes until foamy. Add remaining sugar, butter and eggs and beat until blended, about 1 minute.
Change to dough hook attachment and add 3 cups flour. Beat on low speed 5 minutes or until dough is soft and pulls away from sides of the bowl, adding more flour if necessary.
Turn dough out onto lightly floured surface and knead 1 to 2 minutes or until smooth. Place in oiled bowl and cover. Let rise until doubled, about 1 hour.
Blackberry filling:
Meanwhile, in a small bowl, toss together blackberries, sugar, lemon zest, and cinnamon. Let sit 5 minutes. Mash with potato masher.
Line 9-inch cake pan with parchment paper or grease. Place dough onto lightly floured surface and roll to 14 by 8-inch rectangle. Spread blackberry mixture over dough within 1/2 inch of edges. Top with pecans. Roll up into a log using long side of dough. Cut crosswise into 8 or 10 equal pieces and arrange in cake pan. Cover and let rise 1 hour or until about 1 1/2 times larger.
Preheat oven to 375°F. Bake 15-20 minutes. Tent with a piece of aluminum foil and bake for an additional 10 minutes or until lightly browned.
Glaze:
Whisk together confectioners' sugar, cream cheese, and milk until smooth. Drizzle over warm buns. Let cool about 15 minutes before serving.