One day before, prepare the pound cake. Preheat the oven to 325˚F (165˚C). Grease a loaf pan (9×5-inch) thoroughly with butter.
In a large mixing bowl with an electric mixer fitted with a paddle attachment, beat together butter and cream cheese until light and fluffy, about 5 minutes. Scrap down the paddle and bowl. Add salt, sugar, flour, and baking powder. Mix to combine. Add 1 egg and vanilla extract. Beat well. Add eggs one at a time, scrapping down the paddle and bowl after each time. Mix until just combined.
Transfer the batter to the prepared loaf pan and smooth the top. Wash a butter knife under tap water to wet both sides, then run it into the center of the loaf cake lengthwise (about 1-inch deep into the cake), which will help to create a beautiful crack in the middle.
Bake in the oven for 85 – 90 minutes until golden brown with a nice crack and toothpick comes out clean. Cover the cake with a piece of aluminum foil after 60 minutes. Transfer the pan to a wire rack and cool for 5 minutes. Loosen the sides with a butter knife or offset spatula. Carefully invert the pound cake onto a towel on top of the wire rack. Remove the pan, flip the cake back and place on the rack to cool completely. Wrap in plastic wrap to store at room temperature overnight.
Next day, start with the rhubarb. Preheat the oven to 400˚F (200˚C). Rinse and pat dried. Trim both ends off, and cut into 1½-inch length. Transfer to a 9 x 13 ovenproof dish. Toss with ½ cup sugar. Spread into a single layer. Cover the dish tightly with aluminum foil. Bake in the oven for 10 – 15 minutes, until rhubarb is tender but still hold its shape.
Remove from oven and remove the foil. Let it sit for 20 minutes. Gently transfer the rhubarb to a medium bowl with a slotted spoon. Set aside to cool.
Meanwhile, transfer all the rhubarb liquid into a measuring cup. You should have more than ½ cup. Pour into a small saucepan. Cook on medium-low heat for about 3 – 4 minutes. You should have about ⅓ cup at the end. That’s rhubarb syrup. Set aside to cool.
For the mascarpone whipped cream, in a large mixing bowl with an electric mixer fitted with a whisk attachment, add mascarpone cheese and salt. Beat on low speed for a minute. With the mixer on, slowly add the heavy cream and beat for 30 seconds. Add the powdered sugar. Turn up the speed to medium and beat until medium peaks form. Keep refrigerated until ready to use.
Once everything is cool, cut ½ of the pound cake into ¾-inch cubes. Cut more when it's needed.
To assemble, prepare 1 large trifle bowl or 10 small trifle bowls or 5 mason jars. You can use anything you like as long as it can hold about 11 cups of trifle.
Start with a layer of pound cake, then brush or spoon rhubarb syrups over. You want to use almost all the syrup at the end. Next, add a layer of roasted rhubarb and a layer on fresh strawberries. Cover with a few dollops of mascarpone cream. Depends on the size of your bowl(s), continue with more layers or stop there. To finish, top with a big dollop of mascarpone cream, a couple pound cake cubes & decorate with strawberries. Cover with plastic wrap or lid and keep in the fridge for at least 2 hours before serving.