In a bowl, toss the sliced strawberries with the sugar, lemon juice, salt, and vanilla. Stir gently. Cover and let them sit on the counter for at least 30 minutes while you make the cake.
Preheat your oven to 350°F. Grease an 8-inch round cake pan with butter, line the bottom with parchment , and grease the parchment too. This cake is quite moist, so you really want to set yourself up for success to get it out cleanly.
In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside
In the bowl of a stand mixer (or a big bowl with a hand mixer), beat the softened butter with the granulated sugar on medium-high for 3 to 4 minutes until it looks pale and fluffy. Scrape the bowl down a couple of times
With the mixer on low, slowly stream in the olive oil and beat until fully incorporated. The mixture might look a little broken and that is completely normal, just keep going.
With the mixer still on low-medium (or by hand), add the eggs one at a time, beating well after each one. Add the lemon zest, lemon juice, and vanilla. Beat for 30 seconds until smooth.
Add the flour mixture and the buttermilk in three additions, starting and ending with the flour. So: a third of the flour, half the buttermilk, a third of the flour, the rest of the buttermilk, the rest of the flour. Mix on low just until combined after each addition. Do not overmix
Scrape the batter into your prepared pan and smooth the top. Tap the pan on the counter once or twice to release any big air bubbles. Bake for 50 to 60 minutes, until the top is deep golden, the cake springs back when you press it lightly in the center, and a tester comes out with a couple of moist crumbs but no wet batter!
Let the cake cool in the pan for 15 minutes. Then run a knife around the edge, turn it out onto the rack, peel off the parchment, and let it cool completely. This is a very moist cake so it really needs to be fully cool and set before we move forward with the toppings.
In a clean bowl, beat the softened cream cheese with the powdered sugar on medium until completely smooth, scraping the bowl as needed. Add the vanilla and beat for another 30 seconds. In a separate bowl, whip the cold heavy cream to medium-soft peaks. Fold the whipped cream into the cream cheese mixture in three additions, gently, with a spatula. Pop it in the fridge until you are ready to assemble
Once the cake is fully cool, set it on your serving plate or stand. Pile the cream cheese mousse on top and swoop it around with the back of a spoon or a small offset spatula. You want it generous, so do not be shy. Spoon the macerated strawberries (trying your best not to add the juice that is sitting at the bottom of the bowl) on top of the cream cheese mousse.
Save the syrup and pour it over each slice individually when serving!
This cake is best eaten within an hour of assembling. If you need to make it ahead, you can frost it and chill it covered in the fridge for up to 4 hours, but add the strawberries last so the cake doesn't get soggy