In a saucepan, whisk together the sugar and corn starch.
In a food processor or blender, process the strawberries until smooth, about 1 minute. Transfer to saucepan with sugar mixture and stir to combine.
Heat over medium-low heat, stirring constantly until mixture begins to thicken, about 3-5 minutes. Remove from heat and stir in the lemon juice.
Transfer mixture to a glass bowl and let cool for 10 minutes.
For the cake:
Preheat the oven at 350°F. Grease a 10 cup Bundt pan or a 10 inch loaf pan.
In the bowl of a stand mixer fitted with the paddle attachment, cream the butter and sugar until lighter in color and smooth texture (5min). Beating on medium, start adding 1 egg at a time, followed by the vanilla.
In a separate bowl, combine the flour, salt, baking powder and baking soda. Alternate adding the dry ingredients and the sour cream, in 3 additions, beginning and ending with the dry ingredients.
Pour 1/2 of the batter into the prepared pan.
Using a teaspoon, make 8 dollops of the Strawberry Swirl mix and with a butter knife, make swirls around the cake without over-mixing. Repeat the same process one more time.
Bake for 45-50 minutes, until a toothpick inserted in the center (or sides if using a Bundt pan) comes out clean (internal temp should be 190°F or higher). Time will vary depending on your oven. Let cool in the pan for 15 minutes before transferring to a cooling rack.
For the Icing:
Start by sifting the powdered sugar into a large bowl.
Add 1 tablespoon of lemon juice, and a couple of tablespoons of boiling water.
Work a spoon against the sides of the bowl, getting rid of clumps until reaching a desired consistency. If it’s too thick, add 1 tablespoon of boiling water at a time. If it’s too runny, add 1/4 cup powdered sugar.
Spoon (or transfer to a piping bag without a tip) onto cake, going around the top, rotating the cake until it glides down the sides.
Decorate with fresh strawberries and spring flowers.