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1
Preheat oven to 450F.
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2
Unfold crust in 9-inch-diameter tart pan with removable bottom.
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3
Press crust onto bottom and up sides of pan.
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4
Fold overhang in and press, forming high-standing rim 1/2 inch above pan sides.
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5
Pierce all over with fork.
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6
Bake crust until set and pale golden, about 10 minutes.
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7
Cool in pan on rack.
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8
Reduce oven temperature to 350F.
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9
Grate peel from 2 oranges (orange part only); place in small saucepan.
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10
Cut pith from oranges; discard.
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11
Working over same pan, cut between membranes to release orange segments into pan.
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12
Add 1/4 cup sugar, 1/4 cup water and lemon juice.
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13
Bring to boil.
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14
Reduce heat; simmer until mixture is thickened and segments have fallen apart, stirring often, about 22 minutes.
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15
Cool to room temperature.
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16
Mix cornstarch and 1 cup sugar in medium bowl.
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17
Beat in butter.
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18
Add egg; beat until fluffy.
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19
Stir in orange mixture and Grand Marnier (mixture will look curdled).
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20
Spoon into crust.
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21
Bake tart until set, about 45 minutes.
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22
Cool on rack.
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23
(Can be made 1 day ahead.
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24
Cover; chill.)
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25
Garnish with orange slices.
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26
Serve cold or at room temperature.