Add the cherries, sugar, lemon zest & 1 tbsp. of lemon juice to a small saucepan. Set the mixture over medium heat, stirring occasionally. Lightly mash the cherries as they soften.
In a small bowl, mix together the corn starch and the remaining 1 tbsp. of lemon juice. Allow the cherry mixture to come to a simmer. Then, while constantly stirring the jam, pour in the corn starch slurry. Continue to mix the jam until it thickens, then remove it from the heat.
Set the jam aside until you're ready to assemble the bars. Allow the brownie to completely cool to room temperature before assembling the bars.
Pull out the ice cream ~10 minutes before using it to allow it to soften.
Once the brownies have cooled to room temperature, slice them in half to get two even pieces.
Line a 8x4" loaf pan with plastic wrap. Place on half of the brownie upside down into the pan (you may have to press it gently into place.)
Top the brownie with half of the ice cream, alternating scoops of vanilla and chocolate. Then smooth it into an even layer. Add all of the cherry jam on to the ice cream and use a knife to swirl it into the ice cream.
Add the remaining ice cream on top and smooth it into an even layer. Top the ice cream with the other half of the brownie, face up. Cover the loaf pan with plastic wrap and leave it in the freezer to set for at least 4 hours.
Once the bars have set, remove them from the pan, slice them*, then serve and enjoy!