Set an 8-inch cast iron skillet over medium heat.

While the skillet is preheating, combine the milk and lemon juice. Set aside for 5 minutes.

In a large bowl, whisk together the flour, baking soda, and salt. Make a well in the center of the dry ingredients, and pour in the milk/lemon mixture.

Use your hands to knead lightly or a wooden spoon to mix together the wet and dry ingredients just until combined. (Do not overmix, as this can result in a tough texture.) The dough should come together quickly and be very sticky but manageable.

Transfer the sticky dough to a well-floured flat surface. Shape the dough into a 1/2-inch thick circle. Use a floured knife to cut the dough into quarters.

Sprinkle a little flour into the preheated skillet. Transfer the farls to the floured skillet. Cook for 6 minutes on each side. The cooked farls will be slightly charred in places, feel firm to the touch, and sound hollow when tapped lightly. Serve hot.