Preheat oven to 350F.
Line a baking sheet with parchment paper.
In a medium bowl, combine milk and apple cider vinegar and mix.
Let it sit 5-10 minutes until it thickens.
Meanwhile, if your oats aren't already ground, put them in a food processor and pulse for 10-15 seconds or until they are finely ground. Set aside.
In a large bowl, whisk together flour, salt, baking soda, and baking powder.
Cut in the butter using either a pastry cutter or two knives.
Stir in ground oats.
Pour buttermilk/milk and vinegar mixture into the flour.
Stir the dough until it is just combined but still sticky. Place down on a well flour surfaced.
Knead the dough 4 or 5 times.
Pat and shape into a 7 or 8 inch disk.
Place on the baking sheet.
Dust the top of the dough with flour.
With a large knife, cut an "X" 3/4 inch deep into the dough.
Bake for 50-60 minutes, until the bread is golden and a knife inserted in the middle comes out clean.
Allow to cool on a wire rack.