Preheat the oven to 350 degrees F. Line muffin tins with liners.
Prepare the crumb mixture first: In a small bowl, mix all-purpose flour, sugar, and cinnamon. Mix in butter. It will be very crumbly. Use your hands to mix if you like. Set aside.
Prepare the cream cheese filling: Mix cream cheese, sugar, and vanilla with an electric mixer. Beat until smooth. If the cream cheese is at room temperature, it will blend smoothly with no lumps. Set aside.
Now for the muffin part: In a mixing bowl, combine the first four dry ingredients.
In a second bowl, cream together the butter, sugar, and oil until smooth.
Add the egg, yogurt, and vanilla extract to the sugar mixture and mix well.
Slowly add the dry mixture to the wet mixture.
Toss the chopped rhubarb and strawberries with 1 tablespoon flour. Add the rhubarb and strawberries to the batter and lightly mix in. Do not overmix.
Fill the muffin tins. Use a ¼-cup scoop to fill the liners. Fill them until they are ⅔ full.
Drop 1 tablespoon of the cream mixture on the top of each muffin. I like to make a small indent on the top of the muffin to add the cream cheese.
Sprinkle crumb mixture on top of muffins with a small spoon. Sprinkle it evenly over all of the muffins.
Bake for about 15-20 minutes until the muffins are golden brown on top and a toothpick inserted in the center of the muffin comes out clean. Do not overbake.
Remove muffins carefully from the muffin pan and place on a wire rack to cool for at least 5 minutes.