Heat oven to 350. Grease a 9-inch springform pan and cut a parchment round for the bottom.
Toss the strawberries with the cornstarch until the cornstarch is dissolved. Set aside.
Grind the walnuts until they are very finely chopped but not a paste.
In a medium bowl, mix together the walnuts with the flour, baking powder, and salt.
In another bowl, mix together the buttermilk, vegetable oil, orange juice, and vanilla.
Put the flat beater on your standing mixer. Add the eggs and the sugar to the bowl. Mix on medium high speed for 5 minutes. The batter will be very light colored and flow off the beater in a stream.
Turn the mixer to low. Begin adding the flour and buttermilk mixtures in turn. Start with 1/3 of the flour, then 1/2 of the buttermilk, and continue 1/3, 1/2, 1/3. Be careful not to overmix and only mix just enough to incorporate each addition.
Spread 1/3 of the batter onto the bottom of the prepared springform pan.
Top the batter with 1/2 of the strawberries, spreading them out over the surface.
Add the remaining batter and smooth it out over the top. Then add the remaining berries, pressing them in a bit so they are sitting in the batter.
Bake for 50-55 minutes, or until a skewer comes out clean or until a thermometer reads between 205-210F.
Let rest on a cooling rack for about 15 minutes. Then remove the ring of the springform pan and let it cool completely.
To serve move the cake onto a serving platter (removing the pan base) and dust with confectioners' sugar.