Preheat the oven to 400 degrees. Grease or spray a jumbo muffin pan with nonstick spray. Spray the cups and the top of the pan liberally.
Whisk flour, baking powder and salt together in a mixing bowl.
In a separate bowl cream butter and sugar. Add oil and eggs and mix.
Combine milk and lemon juice in a small bowl. Add milk to wet ingredients and mix.Mix in sour cream.
Add flour mixture to wet ingredients and stir by hand just until combined (DO NOT overmix).Fold in blueberries.
Divide batter evenly and scoop into the jumbo muffin pan (makes 6 muffins).Bake at 400 degrees for 5 minutes.Reduce oven temp to 375 degrees and bake an additional 25-28 minutes. Muffins will be golden on the top and if you insert a toothpick it should come out clean.
Allow muffins to cool in the pan for 10-15 minutes before transferring to a wire cooling rack. To remove the muffins from the pan, use a butter knife to loosen the edges. Muffins should release easily if the pan was properly prepared.
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Notes
Wrap the baked and cooled jumbo muffins individually in plastic wrap to keep the muffins fresh for up to 5 days! They’ll be even softer on day 2.