Preheat oven to 350F. Grease and flour three 8" cake rounds and line with parchment.
In a medium bowl, whisk flour, baking powder, and salt until well combined. Set aside.
Using a stand mixer fitted with a paddle attachment, cream butter and sugar on med-high until pale and fluffy (approx 3mins).
Reduce speed and add eggs one at a time fully incorporating after each addition. Add vanilla.
Alternate adding flour mixture with buttermilk, beginning and ending with flour (3 additions of flour and 2 of milk). Fully incorporating after each addition.
Spread batter evenly between the prepared pans and smooth the tops.
Bake for about 30 mins or until a toothpick inserted into the center comes out mostly clean.
Place cakes on wire rack to cool for 10mins then turn out onto wire rack to cool completely.
Place quartered strawberries and sugar into a medium bowl. Stir to combine. Place in fridge and let sit for 15mins (up to overnight).
Drain strawberries before using in cake. Reserve syrup to drizzle on cake layers during assembly if desired.
Mascarpone Whipped Cream:
Place mixer bowl and whisk into the fridge or freezer to chill.
Pour cold cream into the bowl and whip on high until stiff peaks form. Set aside.
In a separate bowl, beat mascarpone until smooth. Add sugar and beat until combined*
Combine whipped cream and mascarpone mixture until smooth and stiff.*
Divide mascarpone cream into 3 equal portions.
Place one layer of cake on a cake stand or serving plate. Drizzle with reserved strawberry syrup if desired.
Roughly spread 1/3 of the mascarpone cream over the top of the layer. I used the back of a large spoon to do this.
Place 1 1/2 cups of quartered strawberries on top. Repeat with remaining layers leaving the top layer just with the mascarpone cream.**
Refrigerate until serving. Serve same day.
* Be careful not to over beat as the mascarpone will curdle.** I found it easiest to do each individual layer separately, chill them all for 15mins, then stack. This amount of strawberries is enough to cover all 3 layers. If you prefer to leave the top layer like I did, you'll need 3 cups of quartered berries total.