In a measuring cup, whisk together the milk and lemon juice and set aside for 10 minutes.
Line a 12-cup muffin tin with muffin liners
In a large bowl, whisk together the flours, baking powder, baking soda, and salt.
In a medium bowl, whisk together the sugar, milk, melted butter, oil, yogurt, and eggs until completely combined. Pour into the dry ingredients and gently mix until combined. Fold in the rhubarb pieces until just incorporated.
Preheat the oven to 375℉. Divide the batter evenly between the muffin cups. Let the batter rest while the oven heats.
Place the muffin tin in the oven and bake for about 20 minutes, until a tester inserted in a muffin comes out clean. Let the muffins cool for 5 minutes in the tin and then place them on a wire rack to cool completely.