Preheat your oven to 350°F (175°C). Grease and flour a standard 9x5 inch loaf pan, or line it with parchment paper.

In a medium bowl, whisk together the flour, baking soda, salt, and cinnamon. Set aside.

In a large bowl, cream together the softened butter and granulated sugar with an electric mixer until light and fluffy (about 3 minutes). Beat in the eggs one at a time, mixing well after each addition, then stir in the vanilla extract.

Alternately add the dry ingredients and the milk to the wet ingredients, beginning and ending with the dry mixture (add in three additions of dry, two of milk). Mix only until just combined; do not overmix.

Gently fold in the chopped rhubarb pieces using a spatula. Pour the batter evenly into the prepared loaf pan.

Bake for 50 to 60 minutes, or until a wooden skewer inserted into the center comes out clean. If the top starts browning too quickly, loosely tent with foil for the last 15 minutes.

Let the bread cool in the pan for 10 minutes before carefully transferring it to a wire rack to cool completely.

For the glaze: Whisk the powdered sugar and milk/lemon juice until smooth. Drizzle over the cooled bread just before slicing and serving.