In a saucepan, cook peaches with sugars, cinnamon, cornstarch, and lemon juice until thickened (5–7 mins). Let cool.
In a bowl, mix flour, brown sugar, cinnamon, salt. Cut in butter until crumbly. Chill topping.
Preheat oven to 350°F (175°C). Grease and flour a bundt pan.
Cream butter and sugar. Add eggs one at a time, then vanilla.
Whisk dry ingredients in a separate bowl. Alternate adding dry mix and milk to batter.
Pour half the batter into the pan. Layer peach filling. Add remaining batter. Top with crumb mixture.
Bake 60–70 minutes until a toothpick comes out clean. Cool 15 mins in pan, then fully on rack.