In a small bowl, mix together the streusel topping with a spoon. Once it starts to combine, use your hands to have the mixture become crumbly and dry; set aside.
Position the rack in the center of the oven and preheat the oven to 425°F. Spray the muffin tins with nonstick baking spray or line with paper muffin cups.
In a small bowl, mix together the streusel topping; set aside.
Place the pitted and cubed peaches in a medium size bowl, toss with 1 teaspoon of lemon juice and cinnamon. In a small skillet, add the peaches. Cook on medium heat for a few minutes until the peaches soften a little *(this is an optional step).
In a large bowl, whisk together dry ingredients; set aside.
In another bowl, place all the wet ingredients. Whisk together until combined.
Gently fold the wet ingredients into the dry ingredients. Scrape down the sides of the bowl as folding to combine the ingredients; make sure to not over mix. It’s fine if there are some small lumps.
Add the peaches to the batter and fold in until incorporated.
Fill the prepared tins three-quarters full. Sprinkle the streusel topping on top of each muffin.
Bake the muffins at 425°F for 5 minutes. Reduce the temperature to 350°F and bake for an additional 15 minutes *(the muffins could be ready before 15 minutes, so check on them at around 12 minutes). The muffins are done when a toothpick inserted into the center comes out clean or with a few crumbs remaining.
Set the pan on a wire rack to cool for 10 minutes.