In a stand mixer fitted with a whisk attachment, whip the eggs on medium-high speed until foamy, about 1 minute. With the mixer running, add the sugar in 4 batches, whisking for 2 minutes between each addition. The eggs will look pale, fluffy, and form a thick ribbon when the whisk is lifted from the bowl.
Preheat Belgian waffle maker according to manufacturer instructions. Combine egg whites and cream of tartar in the bowl of a stand mixer fitted with a whisk attachment. Beat on medium-high speed until frothy, then add 2 tablespoons granulated sugar. Increase speed to high and whip until the whites hold soft peaks.
In a shallow bowl, mix the boiling water, instant espresso, and ¼ cup of the rum. Set aside and allow to cool to room temperature. In the bowl of an electric mixer fitted with the whisk attachment or beaters, beat the egg yolks with the salt and ⅔ cup of the sugar on medium speed until the mixture is thick, pale yellow, and forms a ribbon when the whisk is lifted out of the bowl, about Strawberry Jam. Add the chopped strawberries, sugar, and lemon juice to a saucepan. Cook the strawberries, stirring occasionally, at medium-high heat. When the strawberries come to a boil, turn the heat down and continue to cook at medium-low heat. Cook until a thermometer reads between 200 and 220ºF. dBPN8.