Step 1

Make the tart crust: Generously grease a 10-inch tart pan with nonstick spray.

Step 2

In a large nonstick skillet, melt the sugar over low heat, until dissolved, but not caramelized, about 2 minutes. Stir in the marshmallows until completely melted. Turn off the heat.

Step 3

Using a heatproof rubber spatula, add the rice cereal to the marshmallow mixture and stir until completely coated and incorporated.

Step 4

Carefully transfer the cereal mixture to the prepared tart pan. Generously grease your hands with nonstick spray, then use to spread and pat down the mixture into an even layer against the bottom and up the sides of the pan. Transfer the crust to the refrigerator to chill for about 20 minutes, or until ready to fill.

Step 5

Make the rainbow pastry cream: In a medium saucepan, whisk together the sugar, cornstarch, lemon zest and salt.

Step 6

In a large bowl, whisk together the egg yolks and milk. Add the mixture to the saucepan, along with the butter, and bring to a boil over medium heat, whisking constantly. Let boil for 2 minutes, then remove from the heat and stir in the vanilla.

Step 7

Strain the pastry cream through a fine-mesh sieve into a large heatproof bowl.

Step 8

Divide the pastry cream evenly between 6 medium bowls, approximately ¾ cups each. Dye each bowl of pastry cream as follows: to make red, add 10 drops of red food coloring. To make orange, add 10 drops of red and 12 drops of yellow. To make yellow, add 8 drops of yellow. To make green, add 12 drops of green. To make blue, add 10 drops of blue. To make purple, add 10 drops of blue and 10 drops of red. Stir each bowl with a clean whisk or small rubber spatula until evenly colored.

Step 9

Assemble the tart: Fill the cereal crust with the colored pastry cream in even lines, starting with red, then orange, yellow, green, blue, and purple. Return the tart to the refrigerator to chill for at least 1 hour, or overnight.

Step 10

Just before serving, decorate the tart with the color-coordinating fruits: strawberries and cherries over the red cream, mango over the orange, pineapple over the yellow, kiwi over the green, blueberries over the blue, and blackberries and dragon fruit over the purple.

Step 11

Slice and serve.

Step 12

Enjoy!